adt-manual: Updated some hard-coded distro values

I found four occurances of "1.8" used in manual.  These needed
to be set to "&DISTRO;" so that they resolve to the latest
YP release.

(From yocto-docs rev: 9db8a2a04085623588e51740a45ee58c500649f6)

Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/dev-manual/dev-manual-model.xml

@@ -939,14 +939,14 @@
                                 For example, if you are using Luna, do the
                                 following:
                                 <literallayout class='monospaced'>
-     $ git checkout luna/yocto-1.8
+     $ git checkout luna/yocto-&DISTRO;
                                 </literallayout>
                                 This puts you in a detached HEAD state, which
                                 is fine since you are only going to be building
                                 and not developing.
                                 <note>
                                     If you are building kepler, checkout the
-                                    <filename>kepler/yocto-1.8</filename>
+                                    <filename>kepler/yocto-&DISTRO;</filename>
                                     branch.
                                 </note>
                                 </para></listitem>
@@ -975,13 +975,13 @@
                                 Be sure to provide the tag name, documentation
                                 branch, and a release name.
                                 Here is an example that uses the
-                                <filename>luna/yocto-1.8</filename> tag, the
+                                <filename>luna/yocto-&DISTRO;</filename> tag, the
                                 <filename>master</filename> documentation
                                 branch, and
                                 <filename>&DISTRO_NAME;</filename> for the
                                 release name:
                                 <literallayout class='monospaced'>
-     $ ECLIPSE_HOME=/home/scottrif/eclipse-poky/scripts/eclipse ./build.sh luna/yocto-1.8 master &DISTRO_NAME; 2>&amp;1 | tee -a build.log
+     $ ECLIPSE_HOME=/home/scottrif/eclipse-poky/scripts/eclipse ./build.sh luna/yocto-&DISTRO; master &DISTRO_NAME; 2>&amp;1 | tee -a build.log
                                 </literallayout>
                                 After running the script, the file
                                 <filename>org.yocto.sdk-</filename><replaceable>release</replaceable><filename>-</filename><replaceable>date</replaceable><filename>-archive.zip</filename>