Native bindings to the ANGLE_texture_usage extension.

In some implementations it is advantageous to know the expected usage of a texture before the backing storage for it is allocated. This can help to inform the implementation's choice of format and type of memory used for the allocation. If the usage is not known in advance, the implementation essentially has to make a guess as to how it will be used. If it is later proven wrong, it may need to perform costly re-allocations and/or reformatting of the texture data, resulting in reduced performance.

This extension adds a texture usage flag that is specified via the TEXTURE_USAGE_ANGLE TexParameter. This can be used to indicate that the application knows that this texture will be used for rendering.