Change internal gid datatype from __gid16_t to __gid32_t
throughout.
* cygwin.din: Export new symbols chown32, fchown32, getegid32,
getgid32, getgrgid32, getgrnam32, getgroups32, initgroups32, lchown32,
setgid32, setegid32, getgrent32.
* grp.cc (grp32togrp16): New static function.
(getgrgid32): New function.
(getgrnam32): Ditto.
(getgrent32): Ditto.
(getgroups32): Change name of internal function from getgroups.
(getgroups32): New function.
(initgroups32): Ditto.
* syscalls.cc (chown32): Ditto.
(lchown32): Ditto.
(fchown32): Ditto.
(setegid32): Ditto.
(setgid32): Ditto.
* uinfo.cc (getgid32): Ditto.
(getegid32): Ditto.
* include/cygwin/grp.h: Remove declaration of getgrgid() and getgrnam().
Declare getgrgid32() and getgrnam32() instead. Declare getgid32().