run-tests.sh, run-test.sh replaced with rnt

rnt/ is https://github.com/roman-neuhauser/rnt.git

currently pointing at 1e2031665aec7ab8b939ecab7f0b9a3dc85ad769,
which is rnt's master ATM.

this testing tool has come the full circle:

  > (cd rnt && git log -1 6bdea)
  commit 6bdea110ebca5b44531d085bea6e733f60627b1b
  Author: Roman Neuhauser <rneuhauser@suse.cz>
  Date:   Tue Jul 17 14:30:16 2012 +0200

      run-tests.sh, run-test.sh from logdemux

      taken from logdemux @ 20d63c4fe95a (not published yet).

current rnt is appreciably slower than the original code
(run-test{,s}.sh dropped in this commit), logdemux tests spend
twice the time in syscalls.  it's also more robust and has
a single, well defined development space, so i don't mind.
logdemux has moved to github, return to hg unlikely
README.rest: mention the license