[dwm] Adapted the pertag patch for 5.0.1

Greetings to all

This is my first attempt to improve-modify existing open source, so please
forgive any
imperfections or errors. I believe the patch i send applied to 5.0.1 to be
free of any bugs.
It is a simple adaptation of the pertag patch which was at the site to the
new version of dwm.
A friend asked me to write it so i worked with the existing patch.
Hopefully the project maintainer can update the web site with this fixed
version.

Thanks in advance.