Still more command-line-argument- and error-message-related bugfixes to svnsync.
Still more command-line-argument- and error-message-related bugfixes
to svnsync.

* subversion/svnsync/main.c
  (initialize_cmd): Check for a missing source URL before segfaulting
    all over it.  Also, make sure the provided paths are URLs.
  (copy_revprops_cmd): Suggest using 'svnsync help' when the revision
    argument is missing.  Also, make sure the destination path is a URL.
  (synchronize_cmd): Make sure the destination path is a URL.
  (main): Stop using SVN_INT_ERR(), which makes all the errors look
    like they came from "svn" instead of "svnsync".

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion