Relax --compatible-version= so it assumes our forward compatibility rules.

Message-ID: 20130322151328.GG3216@lp-shahaf.local

* subversion/svnadmin/svnadmin.c
  (sub_main): Accept any version number within the same major line.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1459849 13f79535-47bb-0310-9956-ffa450edef68
* subversion/libsvn_subr/version.c
  (svn_version__parse_version_string): Reject version strings with negative
    components ("-1.0.0").


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1459852 13f79535-47bb-0310-9956-ffa450edef68