glthread: add option to put autogenerated marshal structures in the header file

This is used when we want to be able to read the calls of autogenerated
functions, or when we want to use the default structure for our custom
marshal functions.

Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/26548>
4 files changed