re PR c++/11512 (Spurious warning for comma-operator in templates)

	PR c++/11512
	* stmt.c (expand_expr_stmt_value): Don't warn about any void
	typed expression.
cp:
	PR c++/11512
	* cvt.c (convert_to_void): Indicate which side of conditional has
	no effects, and rhs of comma operator. Test for no sideeffect
	expressions here and always build a convert expr.
	* init.c (expand_default_init): Convert the init to void.
	* typeck.c (build_x_compound_expr): Do not check for side effects
	here.
	(build_compound_expr): Do not convert lhs when building a
	template.
testsuite:
	PR C++/11512
	* g++.dg/template/warn1.C: New.

From-SVN: r70505