c++: coroutines and range for [PR118491]

c++: coroutines and range for [PR118491]

The implementation of extended range-for temporaries in r15-3840 confused
coroutines, because await_statement_walker and the like get confused by the
EXPR_STMT into thinking that the whole for-loop is a single expression
statement and try to process it accordingly.  Fixing this seems to be a
simple matter of dropping the EXPR_STMT.

	PR c++/116914
	PR c++/117231
	PR c++/118470
	PR c++/118491

gcc/cp/ChangeLog:

	* semantics.cc (finish_for_stmt): Don't wrap the result of
	pop_stmt_list in EXPR_STMT.

gcc/testsuite/ChangeLog:

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