[CentOS] MATE 1.20 test build for CentOS 7 available

Hi everyone,

There's been discussions in the past about updating MATE RPMs in EPEL-7:
https://bugzilla.redhat.com/show_bug.cgi?id=1436260
https://lists.centos.org/pipermail/centos/2019-August/173154.html
(and lots of others...)

As a proof-of-concept, I've written some scripts that clone specific 
commits from the Fedora master branches, and then runs a tool to 
re-apply RPM scriptlets that are required by EL7 but removed from the 
Fedora .spec files.

The scripts are available at:
https://github.com/gebailey/mate-rpms/tree/master/1.20/el7

There's also instructions there if you want to try upgrading to MATE 
1.20 w/o rebuilding them yourself.

If these packages work for others, perhaps we can revisit the idea of 
updating the epel7 branches of the Fedora git repos and submitting an 
official update.

There's nothing here (yet) about building MATE 1.22 (which might require 
a newer gcc for EL7), or building anything on CentOS 8, but thought the 
CentOS 7 users might find this helpful.

-Greg