Doc: items in Issues page context menu

Remove and Show in Editor items were not
documented.

Change-Id: Iec7f2ae6ebc76f715e790de5dbb2e8dbc064b631
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>

doc/src/howto/creator-ui.qdoc

@@ -300,10 +300,14 @@
 
     \image qtcreator-build-issues.png
 
-    Right-clicking on a line brings up a context menu with options to copy
-    the contents and to show a version control annotation view of the line
+    Right-clicking on a line brings up a context menu with options to remove a line, copy
+    its contents, or to show a version control annotation view of the line
     that causes the error message.
 
+    To navigate to the corresponding source code, click an issue or
+    select \gui {Show in Editor} in the context menu. The entry must contain the
+    name of the file where the issue was found.
+
     To jump from one issue to the next or previous one, press \key F6 and
     \key Shift+F6.