Make all_completions use new completion code

This fixes a bug affecting emacs users introduced by 7.2.

Fixes https://github.com/ipython/ipython/issues/11541

IPython/core/completer.py

@@ -1136,8 +1136,12 b' class IPCompleter(Completer):'
 
     def all_completions(self, text):
         """
-        Wrapper around the complete method for the benefit of emacs.
+        Wrapper around the completions method for the benefit of emacs.
         """
+        prefix = text[:text.rfind(".") + 1]
+        return map(lambda c: prefix + c.text,
+                   self.completions(text, len(text)))
+
         return self.complete(text)[1]
 
     def _clean_glob(self, text):