re PR c++/55149 (capturing VLA in lambda)

re PR c++/55149 (capturing VLA in lambda)

	PR c++/55149
	* decl.c (compute_array_index_type): Don't reject VLAs in SFINAE
	context if we're in C++14 mode.
	* tree.c (array_of_runtime_bound_p): Return true for a dependent
	bound that is not potentually constant.
	* cp-tree.h (DECL_VLA_CAPTURE_P, REFERENCE_VLA_OK): New.
	* pt.c (tsubst) [REFERENCE_TYPE]: Check REFERENCE_VLA_OK.
	* semantics.c (build_lambda_object): Don't rvalue a VLA capture.
	(build_capture_proxy): Set REFERENCE_VLA_OK.
	(vla_capture_type): Make it a proper C++ class.
	(add_capture): Set DECL_VLA_CAPTURE_P.  Don't pre-digest the
	initializer.

From-SVN: r200279