done with half of the part of advanced tutorial's first example that deals with C code

doc/advanced/compilation.txt

@@ -4,3 +4,15 @@
 =======================
 Compilation and Linking
 =======================
+
+.. index::
+   single: Linker
+
+.. _linker:
+
+Linker
+======
+
+WRITEME
+
+

doc/tutorials/advanced/ex1/op.txt

@@ -245,11 +245,9 @@ operators (well, pending revision of this tutorial, I guess):
 
    class BinaryDoubleOp(gof.Op):
    
-       def __init__(self, name, fn, gradfnx, gradfny):
+       def __init__(self, name, fn):
            self.name = name
            self.fn = fn
-           self.gradfnx = gradfnx
-           self.gradfny = gradfny
    
        def make_node(self, x, y):
            if isinstance(x, (int, float)):

theano/tensor/basic.py

@@ -319,6 +319,7 @@ class Tensor(Type):
         return """
         Py_XDECREF(py_%(name)s);
         if (!%(name)s) {
+            Py_XINCREF(Py_None);
             py_%(name)s = Py_None;
         }
         else if ((void*)py_%(name)s != (void*)%(name)s) {