add travis config
improve test runner for travis
print errors in pointer comparisons during tests
link against libm and libdl
fix invalid gl_copy_pointer malloc
pedantry in test
add travis status to readme
add pixel convert source formats:

GL_UNSIGNED_SHORT_4_4_4_4
GL_UNSIGNED_SHORT_5_5_5_1
fix recursive display lists
pass window_attribute_list to CreateWindowSurface
add GCW Zero libpreload
add basic glDrawRangeElements implementation
add support for texgen with indices
convert texture uploads directly to RGB ubyte