Relocate GL procs so that they can be implemented in C but the library version still be accessed through a function pointer, and always expose symbols through egl/glGetProcAddress even if GL emulation is disabled.

Conflicts:
	src/library_egl.js
	src/library_gl.js
	src/library_glut.js
	src/library_sdl.js
	src/modules.js
Revert "Relocate GL procs so that they can be implemented in C but the library version still be accessed through a function pointer, and always expose symbols through egl/glGetProcAddress even if GL emulation is disabled."

This reverts commit 4613ad96cd2c2b0f96737e87b1d0edb40ffabafd.