Added doc to extra ops.

doc/library/tensor/extra_ops.txt

+===================================================================
+:mod:`tensor.extra_ops` --  Tensor Extra Ops
+===================================================================
+
+.. module:: tensor.extra_ops
+   :platform: Unix, Windows
+   :synopsis: Tensor Extra Ops
+.. moduleauthor:: LISA
+
+.. automodule:: theano.tensor.extra_ops
+    :members:
+

doc/library/tensor/index.txt

@@ -23,3 +23,4 @@ They are grouped into the following sections:
     shared_randomstreams
     signal/index
     utils
+    extra_ops