/std:c++latest for MSVC, fix bool flip, warn opts

Use `/std:c++latest` for Visual Studio because the XBRZ 1.7 code
requires at least C++17.

Replace the use of `bool++` in `GBALink.cpp` which is now apparently an
error with `bool = !bool` to flip the value.

Use `/W4` to enable a good amount of warnings in Debug mode, and `/W0`
to disable warnings entirely in release modes.

Signed-off-by: Rafael Kitover <rkitover@gmail.com>

CMakeLists.txt

@@ -610,6 +610,14 @@ if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID STREQUAL Clang)
 
     set(CMAKE_C_LINK_EXECUTABLE   "${CMAKE_C_LINK_EXECUTABLE}   ${MY_C_LINKER_FLAGS_STR}")
     set(CMAKE_CXX_LINK_EXECUTABLE "${CMAKE_CXX_LINK_EXECUTABLE} ${MY_C_LINKER_FLAGS_STR}")
+elseif(MSVC)
+    add_compile_options(/std:c++latest)
+
+    if(CMAKE_BUILD_TYPE STREQUAL Debug)
+        add_compile_options(/W4)
+    else()
+        add_compile_options(/W0)
+    endif()
 endif()
 
 # Assembler flags

src/gba/GBALink.cpp

@@ -2925,7 +2925,7 @@ static void UpdateCableIPC(int ticks)
         }
 
         // next cycle
-        transfer_direction++;
+        transfer_direction = !transfer_direction;
     }
 
     if (transfer_direction > linkmem->trgbas && linktime >= trtimeend[transfer_direction - 3][tspeed]) {