Native bindings to the NV_draw_texture extension.

This extension provides a new function, DrawTextureNV(), allowing applications to draw an screen-aligned rectangle displaying some or all of the contents of a two-dimensional or rectangle texture. Callers specify a texture object, an optional sampler object, window coordinates of the rectangle to draw, and texture coordinates corresponding to the corners of the rectangle. For each fragment produced by the rectangle, DrawTextureNV interpolates the texture coordinates, performs a texture lookup, and uses the texture result as the fragment color.