glthread: add support for TexParameteri and SamplerParameteri functions

It's straightfoward except that I had to hack the python scripts to add
"marshal_count", which behaves just like "count" except that "variable_param"
is ignored. ("variable_param" changes the behavior of "count", which I don't
want)

Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3948>
12 files changed