We always return GL_TRUE from the Unmap functions. gl_marshal.py is modified so as not to use "return" in the unmarshal function, which always returns void. Reviewed-by: Zoltán Böszörményi <zboszor@gmail.com> Reviewed-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com> Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9029>