re PR rtl-optimization/54870 (gfortran.dg/array_constructor_4.f90 FAILs)

	PR rtl-optimization/54870
	* tree.h (TREE_ADDRESSABLE): Document special usage on SSA_NAME.
	* cfgexpand.c (update_alias_info_with_stack_vars ): Set it on the
	SSA_NAME pointer that points to a partition if there is at least
	one variable with it set in the partition.
	* dse.c (local_variable_can_escape): New predicate.
	(can_escape): Call it.
	* gimplify.c (mark_addressable): If this is a partitioned decl, also
	mark the SSA_NAME pointer that points to a partition.

From-SVN: r192517