Add image loader for OpenGL Texture with using SDL_image.
Fixed some bugs.
Add some utility functions to Extlib.Std.Prelude .

Conflicts:
	MyOMake
	lib/prelude.ml
	lib/prelude.mli
	src/gl.ml
	src/gl_api.ml
	src/gl_api.mli
	src/gl_api_stubs.c
	src/gl_matrix.ml
	src/gl_matrix.mli
	src/gl_vector.ml
	src/sdl_video.ml
	src/sdl_video_stub.c
	src_bak/sdlut.ml
Revert illegal cherry pick commit.
Fix flag value definitions that are created by flag_printer.