.mailmap: Map "H.Merijn Brand" to "H. Merijn Brand"

This patch was created by searching for duplicates of email addresses
in the shortlog by
    git shortlog -sne |awk '{ print $NF }' |sort |uniq -d

This will yield all email addresses, which are found multiple times within
the shortlog. We can assume that commiters having the same email address
are indeed the same person.

Signed-off-by: Stefan Beller <stefanbeller@googlemail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

.mailmap

@@ -24,6 +24,7 @@ Eric S. Raymond <esr@thyrsus.com>
 Erik Faye-Lund <kusmabite@gmail.com> <kusmabite@googlemail.com>
 Fredrik Kuivinen <freku045@student.liu.se>
 Frédéric Heitzmann <frederic.heitzmann@gmail.com>
+H. Merijn Brand <h.m.brand@xs4all.nl> H.Merijn Brand <h.m.brand@xs4all.nl>
 H. Peter Anvin <hpa@bonde.sc.orionmulti.com>
 H. Peter Anvin <hpa@tazenda.sc.orionmulti.com>
 H. Peter Anvin <hpa@trantor.hos.anvin.org>