* pinfo.h (_pinfo::exists): Declare "new" function.
(_pinfo::kill): Ditto.
* fhandler_termios.cc (tty_min::kill_pgrp): Use _pinfo::exists rather than
proc_exists.
* pinfo.cc (pinfo::init): Ditto. Don't do a low_priority_sleep(0) when looping
to find exec'ed procinfo.
(pinfo::release): Be more careful about unmapping and closing.
* signal.cc (_pinfo::kill): Rename from kill_worker. Accommodate entry into
_pinfo class.
(kill0): Use _pinfo::kill rather than kill_worker.
(kill_pgrp): Ditto. Use _pinfo::exists rather than proc_exists.
* sigproc.cc (_pinfo::exists): Rename from proc_exists.
(pid_exists): Use _pinfo::exists rather than proc_exists.
(remove_proc): Ditto.
* sigproc.h (proc_exists): Delete declaration.