N3639 C++1y VLA support

gcc/
	* gimplify.c (gimplify_vla_decl): Don't touch an existing
	DECL_VALUE_EXPR.
gcc/cp/
	* decl.c (compute_array_index_type): Allow VLAs in C++1y mode.
	(check_array_initializer): Allow VLA init.
	(reshape_init_array_1): Adjust.
	(cp_finish_decl): Check for invalid VLA length.
	* typeck2.c (process_init_constructor_array): Adjust.
	(store_init_value): Use build_vec_init for VLAs.
	* semantics.c (add_capture): Capture VLA as ptr+len.
	(vla_capture_type): New.
	(build_capture_proxy): Rebuild the VLA.
	* typeck.c (build_simple_component_ref): Split out from...
	(build_ptrmemfunc_access_expr): ...here.
	* tree.c (array_of_runtime_bound_p): New.
	* init.c (throw_bad_array_length): New.
	(build_vec_init): Use it.
	* parser.c (cp_convert_range_for): When iterating over a VLA,
	use it directly rather than bind a reference.
	* cp-tree.h: Declare new functions.
libstdc++-v3/
	* libsupc++/new: Add std::bad_array_length.
	* libsupc++/bad_array_length.cc: New.
	* libsupc++/eh_aux_runtime.cc: Add __cxa_bad_array_length.
	* libsupc++/Makefile.in: Build them.
	* config/abi/pre/gnu.ver: Add new symbols.
	* config/abi/pre/gnu-versioned-namespace.ver: Add new symbols.

From-SVN: r198745