libEGL and libGLESv2 have been renamed on latest Raspbian Stretch
version (also included on latest Jessie upgrade).

It seems to be done to avoid conflicts between official Mesa libs and
Broadcomm provided ones.

- Review RPI compilation (core_drop_files not supported)
- Review ImageFormat(), some issues
- GetTextureData() reviewed for RPI

...and reviewed some details

Some people might find this handly

...to avoid issue on Arch Linux

We need to grab the OS name before determining what the path should be.

According to Man Pages, timespec with std=c99 needs "_POSIX_C_SOURCE 199309L". Due a some kind of bug, "#define _POSIX_C_SOURCE 199309L" doesn't work, so we must use "-D_POSIX_C_SOURCE=199309L" in compiler options.

Also reviewed issue with stdbool when compiling with clang

Function names, code formatting...

BMFont loading has been improved to support unordered chars and extended
characters (up to 255)