c++: change implementation of -frange-for-ext-temps [PR118574]

c++: change implementation of -frange-for-ext-temps [PR118574]

The implementation in r15-3840 used a novel technique of wrapping the entire
range-for loop in a CLEANUP_POINT_EXPR, which confused the coroutines
transformation.  Instead let's use the existing extend_ref_init_temps
mechanism.

This does not revert all of r15-3840, only the parts that change how
CLEANUP_POINT_EXPRs are applied to range-for declarations.

	PR c++/118574
	PR c++/107637

gcc/cp/ChangeLog:

	* call.cc (struct extend_temps_data): New.
	(extend_temps_r, extend_all_temps): New.
	(set_up_extended_ref_temp): Handle tree walk case.
	(extend_ref_init_temps): Cal extend_all_temps.
	* decl.cc (initialize_local_var): Revert ext-temps change.
	* parser.cc (cp_convert_range_for): Likewise.
	(cp_parser_omp_loop_nest): Likewise.
	* pt.cc (tsubst_stmt): Likewise.
	* semantics.cc (finish_for_stmt): Likewise.

gcc/testsuite/ChangeLog:

	* g++.dg/coroutines/range-for1.C: New test.