mesa: Remove exec thunks from the dlist.c module.

mesa: Remove exec thunks from the dlist.c module.

These were introduced in 2000 during a rework of the TNL module (commit
cab974cf6c2dbfbf5dd5d291e1aae0f8eeb34290), though I'm having a hard time
finding an instance there of one of these Exec functions being changed
at runtime.

Regardless, as far as I can tell now, these functions don't get changed,
by grepping for calls to SET_* to change the dispatch table (we do change
functions in GLvertexformat at runtime, but those don't overlap with
this set of functions).  Remove them and just let them be initialized to
the same functions as are in the Exec table.

Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>