Add support for GL_ARB_get_program_binary (core in OpenGL 4.1)

Extension is documented at:
https://www.opengl.org/registry/specs/ARB/get_program_binary.txt

This extension adds support for caching compiled program binaries and loading
them back from direct binary data.
Support has been added by adding appropriate OpenGL enumerations and the:
Binary(), Parameteri(), GetBinary() methods to the Program type.