(momentary_function_firstobj): New variable.

(momentary_function_firstobj): New variable.

(init_obstack): Set it.
(save_tree_status): Save it and set it.
(restore_tree_status): Use it and restore it.
(permanent_allocation): New parameter function_end.  Clear
momentary_obstack to momentary_function_firstobj if true.
(preserve_initializer): Set base field of every momentary
level on the momentary stack to new momentary_firstobj.
(pop_momentary): Only free back to previous base.

From-SVN: r6725