Bug 12479 - [SIGNED-OFF] Update mailmap for master

Bug 12479 - [SIGNED-OFF] Update mailmap for master

Just wanted to add a mailmap entry so that GitStats merges together
the commits I made as "David <dcook@prosentient.com.au>" versus
"David Cook <dcook@prosentient.com.au>".

Also increases accuracy if myself or others does a git shortlog...

_TEST PLAN_

Before applying:

1) Run 'git shortlog --author="dcook@prosentient.com.au"'
2) Note two entries: one for "David" and one for "David Cook".

3) Apply patch

4) Repeat step 1
5) Note only one entry for "David Cook"

Signed-off-by: Magnus Enger <digitalutvikling@gmail.com>
Works as advertised.

Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>