c++: reduce temporaries in ?:

c++: reduce temporaries in ?:

When the sides of ?: are class prvalues, we wrap the COND_EXPR in a
TARGET_EXPR so that both sides will initialize the same temporary.  But in
this case we were stripping the outer TARGET_EXPR and conditionally creating
different temporaries, unnecessarily using extra stack.  The
recently added TARGET_EXPR_NO_ELIDE flag avoids this.

gcc/cp/ChangeLog:

	* call.cc (build_conditional_expr): Set TARGET_EXPR_NO_ELIDE on the
	outer TARGET_EXPR.

gcc/testsuite/ChangeLog:

	* g++.dg/tree-ssa/cond-temp1.C: New test.