Updated to the latest version (3.4) of ACL2 and did some
reorganization and addition to support regression testing.

Pathnames only need to be edited in one place now:
.acl2holrc.bash

Edited and added README files. In particular, tests/README explains
how to run the new tests.

Deleted lisp/defaxioms.lisp.trans, an updated version of which is now
in tests/round-trip/gold/axioms.lisp (corresponding to ACL2 Version
3.4).