removing completely insane and purposeless 64x horizontal scaling which is then reversed by a custom transform matrix.  What were you thinking??

Reverting to using the identity matrix (although technically it isn't necessary to set this explicitly at all since it's used by default)
Avoiding unloading the Freetype library and typeface during texture_font_load_glyphs() only to immediately load it again to calculate the kerning.

Explanation: texture_font_generate_kerning() is called only in one place in the entire library, and that's inside texture_font_load_glyphs().  Moving it to before the cleanup of library and face allows us to avoid a costly and completely pointless unload followed by reload.  texture_font_generate_kerning() is not declared in the headers so there is no risk of it being called elsewhere, so this change has no risk of breaking anything in any existing code.  A pointer to the existing face is passed along instead.
adding optional GL_ALPHA format as an alternative to the newly added GL_RED

Older versions of OpenGL do not support GL_RED but newer ones still do support GL_ALPHA.  Rather than switching the whole thing to a deprecated format (which requires changes to the shaders also) for the sake of compatibility, I'm instead adding an #ifdef switch.
adding brief documentation to the defines used in texture_atlas_upload