Add memory management adapter functions

LibPNG builds Zlib with Z_SOLO, so it won't default to the use of the
system memory manager. Stupid.
Updates to VS project
Add GL context flag and error logging

Windows is much more strict about the availability of the OpenGL context,
so all GL objects not confirm before using it.

Also, Windows has no stderr / cerr capability, so a logging mechanism is
put in place instead.
The afore-mentioned logging mechanism