Concurrent use bug

[Raymond Venneker]

L.S.

When starting up GRASS it checks for existance of a file $HOME/.gislock.
If found it holds the pid of the GRASS session currently running and a
diagnostic is printed (... concurrent use not allowed) followed by an exit.

However, I can start up GRASS from another machine without problems [provided
there is no process with the same pid as GRASS on the other machine] 

If concurrent use is really that awful, the checking mechanism should be
improved.

Raymond