configure.in moved to configure.ac, to make things completely obvious.
Removed m4/largefile.m4, which is provided by ac2.5, and add Makefile.am for that dir.
Updated README.CVS to reflect this.
git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@1082 35c25a1d-7b9e-4130-9fde-d3aeb78583b8
