Decouple --without-libarchive and HAVE_ARCHIVE_H

Decouple --without-libarchive and HAVE_ARCHIVE_H

To aid bootstrapping, it would be useful to be able to build e2fsprogs
without archive.h as otherwise there is a build dependency loop with
libarchive. If archive.h is not present, add the missing forward
declarations (as opaque structs) and preprocessor definitions and
typedefs. Since this allows building e2fsprogs with libarchive support
even without the archive.h header present on the system, we cannot check
HAVE_ARCHIVE_H anymore to decide whether to build with libarchive
support or not. So if --without-libarchive is passed to ./configure,
CONFIG_DISABLE_LIBARCHIVE gets set and later checked to decide about
libarchive support.

Addresses-Debian-Bug: #1078693
Signed-off-by: Theodore Ts'o <tytso@mit.edu>