Remove autom4te.cache when doing make distclean.

We can't specify it in DISTCLEAN_TARGETS because it is a directory.
Perhaps we could modify DISTCLEAN_TARGETS to delete dirs too, but
that's outside the scope of what Thom (or I) want to deal with now.

Submitted by:	Thom May <thom@planetarytramp.net>
Reviewed by:	Justin Erenkrantz


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@94922 13f79535-47bb-0310-9956-ffa450edef68