scripts/add_maintainers.pl: New script

scripts/add_maintainers.pl: New script

This provides a much better workflow when using git format-patch and
git send-email, with get_maintainer.pl.

The tool covers step 2 of the following workflow

  Step 1: git format-patch ... -o <patchdir> ...
  Step 2: ./scripts/add_maintainers.pl -d <patchdir>
          This overwrites  *.patch files in <patchdir>
  Step 3: git send-email -to xen-devel@lists.xenproject.org <patchdir>/*.patchxm

I manually tested all options and the most common combinations
on Mac.

Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: George Dunlap <George.Dunlap@eu.citrix.com>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Julien Grall <julien.grall@arm.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Tim Deegan <tim@xen.org>
Cc: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: Lars Kurth <lars.kurth@citrix.com>
Release-acked-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
Acked-by: Lars Kurth <lars.kurth@citrix.com>
Acked-by: George Dunlap <george.dunlap@citrix.com>