libstdc++: Fix Python deprecation warning in printers.py
python/libstdcxx/v6/printers.py:1355: DeprecationWarning: 'count' is passed as positional argument
The Python docs say:
Deprecated since version 3.13: Passing count and flags as positional
arguments is deprecated. In future Python versions they will be
keyword-only parameters.
Using a keyword argument for count only became possible with Python 3.1
so introduce a new function to do the substitution.
libstdc++-v3/ChangeLog:
* python/libstdcxx/v6/printers.py (strip_fundts_namespace): New.
(StdExpAnyPrinter, StdExpOptionalPrinter): Use it.