Lock token syntax

[Pill, Juergen]

What do you think of following change to the lock token syntax:

currently the lock token is a string consisting of binary data.

If we would add say at the very beginning a pre-fix string say "slide",
illegal lock token could be discovered during the parseRequest method and
would not enter the say unlock method, which would enlist some stores until
it finds that the lock token is invalid.

This seams to be a very small change, change the creation and parsing of the
lock token.

Best regards

juergen