Fixed some warnings during doc generation

doc/install.txt

@@ -394,7 +394,7 @@ Windows V1 (Installing from Scratch)
   You can keep the default install options (except for the installation directory).
 
 - Install Mercurial. You can download it
-  `here <http://mercurial.selenic.com/downloads>`_. You may get either the command
+  `here <http://mercurial.selenic.com/downloads>`__. You may get either the command
   line Windows version or the TortoiseHG GUI version: it does not matter as
   far as installing Theano is concerned.
 
@@ -450,7 +450,7 @@ compile GotoBLAS2 (ATLAS may work too, but was not tested, and is
 usually reported to be slower and more difficult to compile -- especially
 on Windows).
 GotoBLAS2 can be downloaded
-`here <http://www.tacc.utexas.edu/tacc-projects/gotoblas2/downloads>`_
+`here <http://www.tacc.utexas.edu/tacc-projects/gotoblas2/downloads>`__
 after registering on the website (we tested v1.13).
 To compile it, you will also need to install MSYS and Perl,
 as described below.
@@ -538,8 +538,7 @@ Windows: Using the GPU
 
 Please note that these are tentative instructions (we have not yet been able to
 get the GPU to work under Windows with Theano).
-Please report your own successes / failures on the
-`theano-users <http://groups.google.com/group/theano-users>`_ mailing list.
+Please report your own successes / failures on the `theano-users`_ mailing list.
 
 Those are instructions for the 32-bit version of Python (the one that comes
 with Python(x,y) is 32-bit).