re PR c/64279 (Warning missing for "(cond) ? A : A" / if(cond) expr1; else expr1; // same expression in if and else branch)

	PR c/64279
	* c-common.h (do_warn_duplicated_branches_r): Declare.
	* c-gimplify.c (c_genericize): Walk the function tree calling
	do_warn_duplicated_branches_r.
	* c-warn.c (expr_from_macro_expansion_r): New.
	(do_warn_duplicated_branches): New.
	(do_warn_duplicated_branches_r): New.
	* c.opt (Wduplicated-branches): New option.

	* c-typeck.c (build_conditional_expr): Warn about duplicated branches.

	* call.c (build_conditional_expr_1): Warn about duplicated branches.
	* semantics.c (finish_expr_stmt): Build statement using the proper
	location.

	* doc/invoke.texi: Document -Wduplicated-branches.
	* fold-const.c (operand_equal_p): Handle MODIFY_EXPR, INIT_EXPR,
	COMPOUND_EXPR, PREDECREMENT_EXPR, PREINCREMENT_EXPR,
	POSTDECREMENT_EXPR, POSTINCREMENT_EXPR, CLEANUP_POINT_EXPR, EXPR_STMT,
	STATEMENT_LIST, and RETURN_EXPR.  For non-pure non-const functions
	return 0 only when not OEP_LEXICOGRAPHIC.
	(fold_build_cleanup_point_expr): Use the expression
	location when building CLEANUP_POINT_EXPR.
	* tree-core.h (enum operand_equal_flag): Add OEP_LEXICOGRAPHIC.
	* tree.c (add_expr): Handle error_mark_node.

	* c-c++-common/Wduplicated-branches-1.c: New test.
	* c-c++-common/Wduplicated-branches-10.c: New test.
	* c-c++-common/Wduplicated-branches-11.c: New test.
	* c-c++-common/Wduplicated-branches-12.c: New test.
	* c-c++-common/Wduplicated-branches-2.c: New test.
	* c-c++-common/Wduplicated-branches-3.c: New test.
	* c-c++-common/Wduplicated-branches-4.c: New test.
	* c-c++-common/Wduplicated-branches-5.c: New test.
	* c-c++-common/Wduplicated-branches-6.c: New test.
	* c-c++-common/Wduplicated-branches-7.c: New test.
	* c-c++-common/Wduplicated-branches-8.c: New test.
	* c-c++-common/Wduplicated-branches-9.c: New test.
	* c-c++-common/Wimplicit-fallthrough-7.c: Coalesce dg-warning.
	* g++.dg/cpp0x/lambda/lambda-switch.C: Move dg-warning.
	* g++.dg/ext/builtin-object-size3.C: Likewise.
	* g++.dg/gomp/loop-1.C: Likewise.
	* g++.dg/warn/Wduplicated-branches1.C: New test.
	* g++.dg/warn/Wduplicated-branches2.C: New test.

From-SVN: r244705