Replace deleted pages with link to new pages

299f0e2d · Francesco Visin · 5621b267 · 299f0e2d · 299f0e2d · 299f0e2d
--- a/doc/tutorial/extending_theano.txt
+++ b/doc/tutorial/extending_theano.txt
+:orphan:
+This page has been moved. Please refer to: :ref:`extending_theano`. 
--- a/doc/tutorial/extending_theano_c.txt
+++ b/doc/tutorial/extending_theano_c.txt
+:orphan:
+This page has been moved. Please refer to: :ref:`extending_theano_c`. 
--- a/doc/tutorial/symbolic_graphs.txt
+++ b/doc/tutorial/symbolic_graphs.txt
+:orphan:
+This page has been moved. Please refer to: :ref:`graphstructures`.