coroutines : Handle for await expressions in for stmts [PR98480].

coroutines : Handle for await expressions in for stmts [PR98480].

The handling of await expressions in the init, condition and iteration
expressions of for loops had been omitted.  Fixed thus.

gcc/cp/ChangeLog:

	PR c++/98480
	* coroutines.cc (replace_continue): Rewrite continue into
	'goto label'.
	(await_statement_walker): Handle await expressions in the
	initializer, condition and iteration expressions of for
	loops.

gcc/testsuite/ChangeLog:

	PR c++/98480
	* g++.dg/coroutines/pr98480.C: New test.
	* g++.dg/coroutines/torture/co-await-24-for-init.C: New test.
	* g++.dg/coroutines/torture/co-await-25-for-condition.C: New test.
	* g++.dg/coroutines/torture/co-await-26-for-iteration-expr.C: New test.