PR c++/44062
	* c-parser.c (c_parser_expression): Mark LHS of a comma
	expression as read if it is a decl, handled component or
	COMPOUND_EXPR with that on the RHS.
	* c-typeck.c (c_process_expr_stmt): Mark RHS of COMPOUND_EXPR
	if it is a decl or handled component.

	* semantics.c (finish_expr_stmt): Don't call mark_exp_read here...
	* cvt.c (convert_to_void): ... but here.  If expr is a COMPOUND_EXPR,
	look at its second operand.

	* c-c++-common/Wunused-var-7.c: New test.
	* g++.dg/warn/Wunused-var-9.C: New test.

From-SVN: r159286