Importing usr.bin/rev

Change-Id: I73c661eb9d4cca5c17b969bb3831541c1f7f9319
Importing usr.bin/machine

Change-Id: I7dd97073e94cbb75fdac7f15c73437c8ce44a606
test75: force child to use a minimum of cpu time

test75 sometimes false-fails if something else is going on
at the same time, presumably because the child doesn't spin
enough to register a nonzero getrusage() cpu time value, as
spin() uses the real time to limit the spinning.

this change forces spin() to do a minimum amount of spinning
before exiting, regardless of scheduling.

Change-Id: I57c63d22969bba418f36bcc8c5ace2b6fb445968
testsh2: allow compiler fallback to gcc

	. lets test work in 'pure DESTDIR' environment

Change-Id: If7d45f01f20bc6369455d706b5ad47d36946fce3