torture: Add a script to edit output from failed runs

This commit adds a script that allows viewing the build and/or
console output from failed rcutorture, locktorture, or rcuperf runs.
This replaces a time-honored but inefficient manual procedure that uses
cut and paste.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Nicholas Piggin <npiggin@gmail.com>