* cygwin.din (pututline): New exported function.
* syscalls.cc (login): Use pututiline().
(setutent): Open utmp as read/write.
(endutent): Check if utmp file is open.
(utmpname): call endutent() to close current utmp file.
(getutid): Enable all cases, use strncmp() to compare ut_id fields.
(pututline): New.
* tty.cc (create_tty_master): Set ut_pid to current pid.