libstdc++: Reformat Python code

Some of these changes were suggested by autopep8's --aggressive
option, others are for readability.

Break long lines by splitting strings across multiple lines, or
introducing local variables to hold results.

Use raw strings for regular expressions, so that backslashes don't need
to be escaped.

libstdc++-v3/ChangeLog:

	* python/libstdcxx/v6/printers.py: Break long lines. Use raw
	strings for regular expressions. Add whitespace around
	operators.
	(is_member_of_namespace): Use isinstance to check type.
	(is_specialization_of): Likewise. Adjust template_name
	for versioned namespace instead of duplicating the re.match
	call.
	(StdExpAnyPrinter._string_types): New static method.
	(StdExpAnyPrinter.to_string): Use _string_types.