Doc: Link to common VCS functions from the Mercurial docs

Change-Id: I4cdf3323e556b4903ff67086367478e0ec22503a
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

doc/src/vcs/creator-vcs-mercurial.qdoc

@@ -39,7 +39,9 @@
 
     Mercurial is a free, distributed source control management tool.
 
-    The \uicontrol Mercurial submenu contains the following additional items:
+    In addition to the standard version control system functions described in
+    \l {Using Common Functions}, you can select the following functions in the
+    \uicontrol Tools > \uicontrol Mercurial submenu:
 
     \table
         \header