Corner case problem fix for when the base template class was
instantiated with %template including the default arguments and
the base class had an explicitly declared constructor.
Swig_symbol_template_deftype() was sometimes incorrectly finding
a constructor instead of a template and thus failing to correctly
expand the template default args. Problem noticed since
9cf049186b where constructors are
stored simply by their name instead of name plus template args.
Probably fixes a few other subtle template problems when a template
class contains default args.
William S Fulton