So in all code in the reflib (ref_gl.dll/.so/.dylib) calls to
ri.Con_Printf(print_level, fmt, ...) have been replaced by calls to
R_Printf(print_level, fmt, ...) which uses ri.Com_VPrintf().
and the changes in the including files for this.
(also removed gl.h includes from local.h, as it's already included in
qgl.h which is included by local.h)
Retexturing support is now always on (you can still switch it off with
the gl_retexturing CVAR), as we don't have the additional libjpeg
dependency anymore.
stb_image is used for tga, jpg and the newly supported png, so the
old tga and jpeg loading code has been removed.
I furthermore cleaned up the somehow messy and possibly slightly broken
retexturing selection code in R_FindImage()
Without this define newer versions of jpeg define a type "bool" as char,
while the MinGW headers define it as "unsigned short". Automake should
have detected that, but...
