Fix handling of default arguments after ignored ones in Python.

Don't skip checking subsequent arguments just because one of them has "in"
typemap with numinputs=0 attribute.

Add a unit test showing the problem which is relatively rare as it doesn't
happen for the class methods and is hidden unless autodoc feature is used for
the global functions.

Closes #377.

Examples/test-suite/python/default_args_runme.py

@@ -110,6 +110,13 @@ def run(module_name):
   default_args.trickyvalue3(10); default_args.trickyvalue3(10, 10)
   default_args.seek(); default_args.seek(10)
 
+  if default_args.slightly_off_square(10) != 102:
+    raise RuntimeError
+
+  if default_args.slightly_off_square() != 291:
+    raise RuntimeError
+
+
 if __name__=="__main__":
   run('default_args')