The uaddr, ufunc, umod and usym functions all seem to work as expected on
FreeBSD, so stop hiding them behind a "#if defined(sun)".

Reported by:	Prashanth Kumar <pra_udupi@yahoo.co.in>
Enable some previously-disabled DTrace tests for umod, ufunc and usym. They
expect the installed ksh binary to be named "ksh", which is not the case
when it's installed on FreeBSD via the shells/ksh93 port. Allow for it to be
"ksh93" as well so that the tests can actually pass.