Use C locale for floats in HLSLParser

[tatokis]

The HLSL parser uses locale-aware functions to parse the shaders, which results in errors parsing all shaders under certain locales.

For example, when a decimal point on a float is denoted by a , instead of a ..
This results in

projectM/presets/presets_milkdrop_200/Geiss - Cosmic Dust 2 - cloud journey.milk(88) : Syntax error: expected ',' near '.'
Failed to parse HLSL(step2) Comp shader

This PR does something similar to dfd335f but for HLSLParser.

[afeinberg]

Some third party libraries may already do this:

folly:::Conv https://github.com/facebook/folly/blob/master/folly/docs/Conv.md
boost::lexical_cast https://www.boost.org/doc/libs/1_42_0/libs/conversion/lexical_cast.htm

[tatokis]

If I understand correctly, using either of those would bring in another dependency, which isn't really a good idea for only this specific thing. I'm also not sure if those libraries support getting the end of the float in the string, which is needed for the parser.
I may be wrong though as I am not familiar with either of those, and I only had a quick glance at the links.

Additionally, as mentioned, the rest of the code does the same thing, which is why I think it's the best course of action.

projectm/src/libprojectM/MilkdropPresetFactory/Parser.cpp

Lines 1285 to 1300 in fd1d235

	int Parser::string_to_float(char * string, float * float_ptr)
	{
	if (*string == 0)
	return PROJECTM_PARSE_ERROR;
	std::istringstream iss(string);
	iss.imbue(std::locale("C"));
	iss >> (*float_ptr);
	if (!iss.fail()) {
	return PROJECTM_SUCCESS;
	}
	(*float_ptr) = 0;
	return PROJECTM_PARSE_ERROR;
	}

[afeinberg]

nit: let the compiler decide for itself if it wants to inline this or not: is my advice.

alternativelhy you can use an anonymous namespace instead of static

// what would be a static before
} // anonymous namespace

[tatokis]

Well, inline is a suggestion to the compiler. It doesn't force it to do anything. The static was there to make inlining it easier, as when used on a function like this. It makes it accessible only inside that source file/translation unit.
I do agree though. It was only done like that because it's used in that specific place.

If you think it's better, I can make it a normal function that's part of the class, private or public.

[revmischa]

Good to merge?

[revmischa]

Ok, thanks a lot for this improvement!