aklog: Tidy header includes

aklog: Tidy header includes

Since we adopted libroken, we get a lot of header includes automatically
from roken.h. Use these, instead of including lots of things multiple
times.

Also add pwd.h to the list of headers that we check for in configure,
and that roken will include if they are available

Change-Id: I61ab95eeca11127a33bb668dddfc24ec6ce7f8f1
Reviewed-on: http://gerrit.openafs.org/4303
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>