This patch removes the am33 port (no other port #includes any files
from it), as previously discussed (see
<https://sourceware.org/ml/libc-ports/2014-01/msg00046.html>).
Autoconf has been deprecating configure.in for quite a long time.
Rename all our configure.in and preconfigure.in files to .ac.
Signed-off-by: Mike Frysinger <vapier@gentoo.org>