mesa: Import a copy of the open-addressing hash table code I wrote.

mesa: Import a copy of the open-addressing hash table code I wrote.

Mesa's chaining hash table for object names is slow, and this should be much
faster.  I namespaced the functions under _mesa_*, to avoid visibility
troubles that we may have had before with hash_table_* functions.

v2: Move .c file to main/, const a few things, clean up loop conditions,
    add/extend some comments.

Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Chad Versace <chad.versace@linux.intel.com>
Acked-by: Kenneth Graunke <kenneth@whitecape.org> (v1)