-- Command: sessionname [NAME]
Rename the current session. Note that for screen -list' the name
shows up with the process-id prepended. If the argument NAME is
omitted, the name of this session is displayed.
_Caution_: Among other problems, the$STY' environment variable
still reflects the old name. Use of this command is strongly
discouraged. Use the `-S' commandline option if you need this
feature. The default is constructed from the tty and host names.