build-sys: reindent AC_ARG_WITH section in acinclude.m4

Change-Id: I80b68eeecf9f72ac7f2ce133d9a5642a67dde22c
Reviewed-on: http://gerrit.openafs.org/10013
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>