S9 EXT  (sys:getpgid integer)  ==>  integer
        (sys:setpgid integer)  ==>  unspecific

SYS:GETPGRP returns the process group ID of the S9 process and
SYS:SETPGRP changes the process group ID of the process.

(sys:setpgrp (sys:getpgrp))  ==>  unspecific
