ENH: use __text_signature__ if pydoc.doc does not reveal a signature.

This allows to support the __text_signature__ property on Python 3.4+
to document C functions.

Author: MSeifert04

numpydoc/numpydoc.py

@@ -114,8 +114,9 @@ def mangle_signature(app, what, name, obj, options, sig, retann):
         return
 
     doc = SphinxDocString(pydoc.getdoc(obj))
-    if doc['Signature']:
-        sig = re.sub(sixu("^[^(]*"), sixu(""), doc['Signature'])
+    sig = doc['Signature'] or getattr(obj, '__text_signature__', None)
+    if sig:
+        sig = re.sub(sixu("^[^(]*"), sixu(""), sig)
         return sig, sixu('')