d: Missed RVO optimization with non-POD structs

d: Missed RVO optimization with non-POD structs

The D front-end semantic pass sometimes declares a temporary inside a
return expression.  This is now detected with the RESULT_DECL replacing
the temporary, allowing for RVO to be done.

	PR d/101273

gcc/d/ChangeLog:

	* toir.cc (IRVisitor::visit (ReturnStatement *)): Detect returns that
	use a temporary, and replace with return value.

gcc/testsuite/ChangeLog:

	* gdc.dg/torture/pr101273.d: New test.