[838/906] gl: Use GL_TEXTURE_2D instead of GL_TEXTURE_RECTANGLE

[838/906] gl: Use GL_TEXTURE_2D instead of GL_TEXTURE_RECTANGLE

We create our textures (in Desktop GL) with GL_TEXTURE_RECTANGLE,
vaapi attempts to bind our texture to GL_TEXTURE_2D which throws a
GL_INVALID_OPERATION error and as thus, no video.

Also, by moving exclusively to GL_TEXTURE_2D and the npot extension
we also remove a difference between the Desktop GL and GLES2 code.

https://bugzilla.gnome.org/show_bug.cgi?id=712287