autoconf: updates and cleanup

autoconf: updates and cleanup

Update autoconf macros to their modern equivalents, according to what
the 'autoupdate' tool does. While we're here, remove automake references
that aren't being used, and remove the obsolete AC_PROG_LIBTOOL in favor
of AFS_LT_INIT.

Change-Id: I71066d6d72f8b1d8663e26fec83ae23d7f73f059
Reviewed-on: https://gerrit.openafs.org/12199
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>