State the specific dependencies for the GUI in the build tutorial.

Remove mention of old Ubuntu release.

doc/user/tutorials/building.txt

@@ -13,17 +13,15 @@ need:
  * http://gmerlin.sourceforge.net/[GAVL library]
  * *NoBug* (see below)
 
+The GUI depends on:
+
+ * http://www.gtkmm.org/en/[gtkmm]
+ * http://cgit.freedesktop.org/xorg/lib/libXv[libXv]
+
 TIP: Generally speaking, when you want to build software, you need the
 _development_ version of the packages, containing the headers and pre-built
 libraries to link against. Usually, these packages are named `-devel` or `-dev`
 
-.Notes for Ubuntu:
-
-On Hardy you need also:
-
- * libgtkmm-2.4-dev
- * libxv-dev
-
 For most Debian based systems, e.g. Ubuntu, you can install these dependencies
 with:
 
@@ -33,6 +31,8 @@ libboost-program-options-dev libboost-regex-dev libgavl-dev libgdl-1-dev \
 libgtkmm-2.4-dev librsvg2-dev libtool libxv-dev scons valgrind
 ------------------------------------------------------------
 
+Optionally, you may also want to install the *gtk2-engines* package.
+
 Build directory
 ---------------