log test records hash of log output
renamed digest test to video test. removed audio testing
added -log output to "regress add" mode. note that this has nothing to
do with the log test. it simply echos new log entries as the appear to
the console, supressing regression progress meters
the note about historical versions also being covered wasn't strictly
needed and was ugly. the LICENCE being in the root file from the very
first commit is sufficient.