-Wduplicated-branches compilation warnings on Linux/X11 builds.

[bruvzg]

Godot version:
3.2 master, 0aefec2

OS/device including version:

Ubuntu 18.04.3 LTS VM (32 and 64-bit)
gcc version 7.4.0 (Ubuntu 7.4.0-1ubuntu1~18.04.1)

Issue description:

scons -j4 p=x11 tools=yes target=debug debug_symbols=yes optimize=speed warnings=extra

Following warnings are raised with aforementioned compiler and build command.

Warnings:

core/image.cpp: In instantiation of 'void _convert(int, int, const uint8_t*, uint8_t*) [with unsigned int read_bytes = 1; bool read_alpha = false; unsigned int write_bytes = 1; bool write_alpha = true; bool read_gray = true; bool write_gray = true; uint8_t = unsigned char]':
core/image.cpp:466:104:   required from here
cc1plus: warning: this condition has identical branches [-Wduplicated-branches]
core/image.cpp: In instantiation of 'void _convert(int, int, const uint8_t*, uint8_t*) [with unsigned int read_bytes = 1; bool read_alpha = false; unsigned int write_bytes = 1; bool write_alpha = false; bool read_gray = true; bool write_gray = false; uint8_t = unsigned char]':
core/image.cpp:467:105:   required from here
cc1plus: warning: this condition has identical branches [-Wduplicated-branches]
core/image.cpp: In instantiation of 'void _convert(int, int, const uint8_t*, uint8_t*) [with unsigned int read_bytes = 1; bool read_alpha = true; unsigned int write_bytes = 1; bool write_alpha = false; bool read_gray = true; bool write_gray = true; uint8_t = unsigned char]':
core/image.cpp:471:104:   required from here
cc1plus: warning: this condition has identical branches [-Wduplicated-branches]
core/image.cpp: In instantiation of 'void _convert(int, int, const uint8_t*, uint8_t*) [with unsigned int read_bytes = 1; bool read_alpha = true; unsigned int write_bytes = 1; bool write_alpha = false; bool read_gray = true; bool write_gray = false; uint8_t = unsigned char]':
core/image.cpp:472:105:   required from here
cc1plus: warning: this condition has identical branches [-Wduplicated-branches]
core/image.cpp: In instantiation of 'void _convert(int, int, const uint8_t*, uint8_t*) [with unsigned int read_bytes = 1; bool read_alpha = false; unsigned int write_bytes = 1; bool write_alpha = false; bool read_gray = false; bool write_gray = true; uint8_t = unsigned char]':
core/image.cpp:476:105:   required from here
cc1plus: warning: this condition has identical branches [-Wduplicated-branches]
core/image.cpp: In instantiation of 'void _convert(int, int, const uint8_t*, uint8_t*) [with unsigned int read_bytes = 1; bool read_alpha = false; unsigned int write_bytes = 1; bool write_alpha = true; bool read_gray = false; bool write_gray = true; uint8_t = unsigned char]':
core/image.cpp:477:105:   required from here
cc1plus: warning: this condition has identical branches [-Wduplicated-branches]
core/image.cpp: In instantiation of 'void _convert(int, int, const uint8_t*, uint8_t*) [with unsigned int read_bytes = 3; bool read_alpha = false; unsigned int write_bytes = 3; bool write_alpha = true; bool read_gray = false; bool write_gray = false; uint8_t = unsigned char]':
core/image.cpp:490:110:   required from here
cc1plus: warning: this condition has identical branches [-Wduplicated-branches]
core/image.cpp: In instantiation of 'void _convert(int, int, const uint8_t*, uint8_t*) [with unsigned int read_bytes = 3; bool read_alpha = true; unsigned int write_bytes = 3; bool write_alpha = false; bool read_gray = false; bool write_gray = false; uint8_t = unsigned char]':
core/image.cpp:495:110:   required from here
cc1plus: warning: this condition has identical branches [-Wduplicated-branches]

Relevant code:

godot/core/image.cpp

Lines 460 to 500 in 0aefec2

	uint8_t *wptr = w.ptr();
	int conversion_type = format | p_new_format << 8;
	switch (conversion_type) {
	case FORMAT_L8 | (FORMAT_LA8 << 8): _convert<1, false, 1, true, true, true>(width, height, rptr, wptr); break;
	case FORMAT_L8 | (FORMAT_R8 << 8): _convert<1, false, 1, false, true, false>(width, height, rptr, wptr); break;
	case FORMAT_L8 | (FORMAT_RG8 << 8): _convert<1, false, 2, false, true, false>(width, height, rptr, wptr); break;
	case FORMAT_L8 | (FORMAT_RGB8 << 8): _convert<1, false, 3, false, true, false>(width, height, rptr, wptr); break;
	case FORMAT_L8 | (FORMAT_RGBA8 << 8): _convert<1, false, 3, true, true, false>(width, height, rptr, wptr); break;
	case FORMAT_LA8 | (FORMAT_L8 << 8): _convert<1, true, 1, false, true, true>(width, height, rptr, wptr); break;
	case FORMAT_LA8 | (FORMAT_R8 << 8): _convert<1, true, 1, false, true, false>(width, height, rptr, wptr); break;
	case FORMAT_LA8 | (FORMAT_RG8 << 8): _convert<1, true, 2, false, true, false>(width, height, rptr, wptr); break;
	case FORMAT_LA8 | (FORMAT_RGB8 << 8): _convert<1, true, 3, false, true, false>(width, height, rptr, wptr); break;
	case FORMAT_LA8 | (FORMAT_RGBA8 << 8): _convert<1, true, 3, true, true, false>(width, height, rptr, wptr); break;
	case FORMAT_R8 | (FORMAT_L8 << 8): _convert<1, false, 1, false, false, true>(width, height, rptr, wptr); break;
	case FORMAT_R8 | (FORMAT_LA8 << 8): _convert<1, false, 1, true, false, true>(width, height, rptr, wptr); break;
	case FORMAT_R8 | (FORMAT_RG8 << 8): _convert<1, false, 2, false, false, false>(width, height, rptr, wptr); break;
	case FORMAT_R8 | (FORMAT_RGB8 << 8): _convert<1, false, 3, false, false, false>(width, height, rptr, wptr); break;
	case FORMAT_R8 | (FORMAT_RGBA8 << 8): _convert<1, false, 3, true, false, false>(width, height, rptr, wptr); break;
	case FORMAT_RG8 | (FORMAT_L8 << 8): _convert<2, false, 1, false, false, true>(width, height, rptr, wptr); break;
	case FORMAT_RG8 | (FORMAT_LA8 << 8): _convert<2, false, 1, true, false, true>(width, height, rptr, wptr); break;
	case FORMAT_RG8 | (FORMAT_R8 << 8): _convert<2, false, 1, false, false, false>(width, height, rptr, wptr); break;
	case FORMAT_RG8 | (FORMAT_RGB8 << 8): _convert<2, false, 3, false, false, false>(width, height, rptr, wptr); break;
	case FORMAT_RG8 | (FORMAT_RGBA8 << 8): _convert<2, false, 3, true, false, false>(width, height, rptr, wptr); break;
	case FORMAT_RGB8 | (FORMAT_L8 << 8): _convert<3, false, 1, false, false, true>(width, height, rptr, wptr); break;
	case FORMAT_RGB8 | (FORMAT_LA8 << 8): _convert<3, false, 1, true, false, true>(width, height, rptr, wptr); break;
	case FORMAT_RGB8 | (FORMAT_R8 << 8): _convert<3, false, 1, false, false, false>(width, height, rptr, wptr); break;
	case FORMAT_RGB8 | (FORMAT_RG8 << 8): _convert<3, false, 2, false, false, false>(width, height, rptr, wptr); break;
	case FORMAT_RGB8 | (FORMAT_RGBA8 << 8): _convert<3, false, 3, true, false, false>(width, height, rptr, wptr); break;
	case FORMAT_RGBA8 | (FORMAT_L8 << 8): _convert<3, true, 1, false, false, true>(width, height, rptr, wptr); break;
	case FORMAT_RGBA8 | (FORMAT_LA8 << 8): _convert<3, true, 1, true, false, true>(width, height, rptr, wptr); break;
	case FORMAT_RGBA8 | (FORMAT_R8 << 8): _convert<3, true, 1, false, false, false>(width, height, rptr, wptr); break;
	case FORMAT_RGBA8 | (FORMAT_RG8 << 8): _convert<3, true, 2, false, false, false>(width, height, rptr, wptr); break;
	case FORMAT_RGBA8 | (FORMAT_RGB8 << 8): _convert<3, true, 3, false, false, false>(width, height, rptr, wptr); break;
	}
	r.release();
	w.release();