svnbrowse: Display the browsing revision number to the right from URL.

* subversion/svnbrowse/svnbrowse.c
  (format_revision_header): New function.
  (view_draw_header): Put formatted revision number into suffix; use the lazy
   approach by concatinating it with double-spaced string for the indentation.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1933123 13f79535-47bb-0310-9956-ffa450edef68