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/default_args.i

@@ -278,3 +278,17 @@ struct ConstMethods {
     } Pointf;
   }
 %}
+
+// Default arguments after ignored ones.
+%typemap(in, numinputs=0) int square_error { $1 = 2; };
+%typemap(default, noblock=1) int def17 { $1 = 17; };
+
+// Enabling autodoc feature has a side effect of disabling the generation of
+// aliases for functions that can hide problems with default arguments at
+// Python level.
+%feature("autodoc","0") slightly_off_square;
+
+%inline %{
+  inline int slightly_off_square(int square_error, int def17) { return def17*def17 + square_error; }
+%}
+

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')