Changes to configure script and OpenGL for Win32

TODO: Need to implement gloffscreen_cgl for Mac.
Added gloffscreen.h and fixed gloffscreen_glx conditional.
Trimed down gloffscreen files, created glo_check_extension, updated the makefile with
architecture conditionals, and modified nv2a according to gloffscreen changes.
Formatting...
More formatting...
Formatting is fun!
Formatting...
Some additiona formatting.
Moved gloffscreen files to gl dir, and the gloffscreen_glx.c. Trimmed gloffscreen_common.c a little. Modified Makefile.target and nv2a.c according to the new gloffscreen files location.
Moved files
fix up copyrights
Don't see the point of exporting glo_init for now
glx stuff not used in windows so don't need to be common?
rescue glo readpixels wrapper. things shouldn't be upside-down ;)
clean up nv2a opengl includes and use glo_readpixels