MultiDrawElementsUserBuf is changed to mean the same thing as
glMultiDrawElementsBaseVertex, but "gl_buffer_object *index_buffer" is
passed via a parameter instead of using the bound GL_ELEMENT_ARRAY_BUFFER.
This skips binding and unbinding the index buffer around every draw
where glthread uploads indices.
Acked-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20624>
Marek Olšák
e97d0b318b