Add external editor mappings to Command Line and Text Edit modes.

This is bound to <C-i> in each of these modes as it is for Insert mode.

--HG--
extra : rebase_source : 846abe669c943637de39a8def11e30d812f01fc2

common/locale/en-US/cmdline.xml

@@ -48,6 +48,14 @@
 
 <h2 tag="cmdline-editing">Command line editing</h2>
 
+<item>
+    <tags><![CDATA[c_<C-i>]]></tags>
+    <spec>&lt;C-i></spec>
+    <description short="true">
+        <p>Launch the external editor. See the <o>editor</o> option.</p>
+    </description>
+</item>
+
 <item>
     <tags><![CDATA[c_<C-c>]]></tags>
     <spec>&lt;C-c></spec>