libstdc++: Refactor Python Xmethods to use is_specialization_of

libstdc++: Refactor Python Xmethods to use is_specialization_of

This copies the is_specialization_of function from printers.py (with
slight modification for versioned namespace handling) and reuses it in
xmethods.py to replace repetitive re.match calls in every class.

This fixes the problem that the regular expressions used \d without
escaping the backslash properly.

libstdc++-v3/ChangeLog:

	* python/libstdcxx/v6/xmethods.py (is_specialization_of): Define
	new function.
	(ArrayMethodsMatcher, DequeMethodsMatcher)
	(ForwardListMethodsMatcher, ListMethodsMatcher)
	(VectorMethodsMatcher, AssociativeContainerMethodsMatcher)
	(UniquePtrGetWorker, UniquePtrMethodsMatcher)
	(SharedPtrSubscriptWorker, SharedPtrMethodsMatcher): Use
	is_specialization_of instead of re.match.