Borrow a few things from the main Tomcat build.xml:

Borrow a few things from the main Tomcat build.xml:
- use general version filter
- automatically set year to the current year
- use patch version property without dot.
  The dot is added when combining it into a version number

I don't know whether the double '@' are intended for the
ant replacement markers in MANIFEST.MF (the outer ones remain
after ant filtering), but that is unchanged from the previous
behaviour.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@895204 13f79535-47bb-0310-9956-ffa450edef68