re PR fortran/49103 (local variables exchange values / wrong code with -O3)

re PR fortran/49103 (local variables exchange values / wrong code with -O3)

	PR fortran/49103
	* tree.h (DECL_NONSHAREABLE): Define.
	(struct tree_decl_common): Change decl_common_unused to
	decl_nonshareable_flag.
	* cfgexpand.c (expand_used_vars_for_block, clear_tree_used):
	Ignore vars with DECL_NONSHAREABLE bit set.
	* tree-cfg.c (gimple_duplicate_bb): Set DECL_NONSHAREABLE
	on stores to automatic aggregate vars.

	* gfortran.dg/pr49103.f90: New test.

From-SVN: r175028