better job searching for the bsdtar binary to test and the gtar binary
to use for inter-operability testing. It should now find the built
(but not installed) binary if there is one, then search for an
installed binary in a number of standard locations.
* New test scripts exercise some basic functionality
* Most header inclusions are now protected (portability)
* read.c now relies on security checks in libarchive instead
of trying to do its own (optimization)
* -p now enabled by default for root, add --no-same-permissions
to disable it
* Comments, minor style fixes.
