Some more work on the release notes.
Some more work on the release notes.

* www/svn_1.6_releasenotes.html
  (news): Generalize the externals improvements entry.
  (externals): New umbrella section, including the file externals improvements
    and shell quoting in externals.


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@876733 13f79535-47bb-0310-9956-ffa450edef68

YueLinHo/Subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion,wbond/subversion,wbond/subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion