Fix obstack use-after-free problems in C frontend, PR69522

Fix obstack use-after-free problems in C frontend, PR69522

c/
	PR c/69522
	* c-parser.c (c_parser_braced_init): New arg outer_obstack.  All
	callers changed.  If nested_p is true, use it to call
	finish_implicit_inits.
	* c-tree.h (finish_implicit_inits): Declare.
	* c-typeck.c (finish_implicit_inits): New function.  Move code
	from ...
	(push_init_level): ... here.
	(set_designator, process_init_element): Call finish_implicit_inits.

testsuite/
	PR c/69522
	gcc.dg/pr69522.c: New test.

From-SVN: r233366