OGLES2 doesn't support uniform booleans so we use macros to make it use
integers in this case. For other platforms, this change should be a
noop.
OGLES2 doesn't like float suffix for constants, remove it as well.
We now link with OpenGL dynamically so symbols are provided by GLAD.
If it's not supported pointer will be null.
OGLES2 should support these functions so they must be removed