Align CMSG buffers to a void* boundary, fixes crash on architectures with strict alignment

CHANGES entry

(cherry picked from commit 17212cf9)
14 jobs for 521-align-cmsg-buffers-v9_12 in 7 minutes and 57 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Precheck
passed precheck:debian:sid:amd64 #55187
amd64 docker linux

00:00:17

 
  Build
passed build:centos:centos6:amd64 #55188
amd64 docker linux

00:02:11

passed build:centos:centos7:amd64 #55189
amd64 docker linux

00:02:19

passed build:debian:sid:amd64 #55190
amd64 docker linux

00:02:29

passed build:debian:sid:i386 #55191
i386 docker linux

00:02:42

 
  Test
passed install:debian:sid:amd64 #55200
amd64 docker linux

00:02:37

passed systemtest:centos:centos6:amd64 #55196
amd64 docker linux

00:04:52

passed systemtest:centos:centos7:amd64 #55197
amd64 docker linux

00:04:42

passed systemtest:debian:sid:amd64 #55198
amd64 docker linux

00:04:50

passed systemtest:debian:sid:i386 #55199
i386 docker linux

00:04:54

passed unittest:centos:centos6:amd64 #55192
amd64 docker linux

00:01:12

passed unittest:centos:centos7:amd64 #55193
amd64 docker linux

00:01:13

passed unittest:debian:sid:amd64 #55194
docker linux amd64

00:01:06

passed unittest:debian:sid:i386 #55195
i386 docker linux

00:01:02