GFXR -- FStream error return handling incorrect

[jzulauf-lunarg]

The return code from various fstream IO calls is being incorrectly conflated with errno. Error return is not errno. Only extern errno is.

Example:

gfxreconstruct/framework/util/platform.h

Line 753 in 633f344

inline bool FileWrite(const void* buffer, size_t bytes, FILE* stream)

FileReadBytes fixed as example:

gfxreconstruct/framework/util/platform.h

Line 828 in 093bf23

inline size_t FileReadBytes(void* buffer, size_t bytes, FILE* stream)