doc: Update URLs to point to gitlab.inria.fr.

documents/contacts.dox

@@ -17,6 +17,6 @@ The following people have been involved in ALTA development:
 </ul>
 
   More information on the project are available on the
-  <a href="https://gforge.inria.fr/projects/alta/">Gforge project webpage</a>
+  <a href="https://gitlab.inria.fr/alta/alta">Inria Gitlab project</a>.
 
 */

documents/install.dox

@@ -5,7 +5,7 @@
 
 To access the sources of ALTA, clone the public [Git][git] repository:
 
-    $ git clone https://gforge.inria.fr/git/alta/alta.git
+    $ git clone https://gitlab.inria.fr/alta/alta.git
 
 ## Dependencies
 

documents/mainpage.dox

@@ -39,7 +39,7 @@ ALTA is free software available under the [Mozilla Public License,
 version 2.0](http://mozilla.org/MPL/2.0/).  The latest release, version
 0.2, can be obtained from the Git repository:
 
-    $ git clone https://gforge.inria.fr/git/alta/alta.git
+    $ git clone https://gitlab.inria.fr/alta/alta.git
     $ git checkout v0.2
 
 See \ref install "the installation instruction" for more information.