make link in the doc work.

doc/library/tensor/signal/conv.txt

@@ -7,8 +7,8 @@
 .. note::
 
     Two similar implementation exists for conv2d:
-    **theano.tensor.signal.conv.conv2d** and
-    **theano.tensor.nnet.conv.conv2d**. The foremer implements a traditional
+    :func:`signal.conv2d <theano.tensor.signal.conv.conv2d>` and
+    :func:`nnet.conv2d <theano.tensor.nnet.conv.conv2d>. The former implements a traditional
     2D convolution, while the latter implements the convolutional layers
     present in convolutional neural networks (where filters are 3D and pool
     over several input channels).