memory alloc: Add IMAGE and BUFFER alloc info structures

memory alloc: Add IMAGE and BUFFER alloc info structures

For images have the tests fill in the IMAGE_ALLOC structures.  For buffers
this is not yet done.

Conflicts:
	demos/cube.c
	demos/tri.c
	include/xgl.h
	tests/init.cpp
	tests/xgltestbinding.cpp