Re-implement Python -fastproxy option.

The previous implementation failed with Python 3 and abstract base clases.
The new implementation replaces the Python 2 implementation using new.instancemethod with C API PyMethod_New to match the equivalent Python 3 implementation which uses PyInstanceMethod_New.

Closes #1310

Examples/test-suite/python/autodoc_runme.py

@@ -13,15 +13,20 @@ def check(got, expected, expected_builtin=None, skip=False):
 def is_new_style_class(cls):
     return hasattr(cls, "__class__")
 
-def is_fastproxy(module):
-    return "new_instancemethod" in module
+def is_fastproxy():
+    fastproxy = True
+    try:
+        from autodoc import _swig_new_instance_method
+    except ImportError:
+        fastproxy = False
+    return fastproxy
 
 if not is_new_style_class(A):
     # Missing static methods make this hard to test... skip if -classic is
     # used!
     sys.exit(0)
 
-if is_fastproxy(dir()):
+if is_fastproxy():
     # Detect when -fastproxy is specified and skip test as it changes the function names making it
     # hard to test... skip until the number of options are reduced in SWIG-3.1 and autodoc is improved
     sys.exit(0)