s/usg5-4.h:

s/usg5-4.h:
(NSIG): Remove.
(NSIG_MINIMUM): New macro.
s/gnu-linux.h, s/hpux.h, s/iris3-5.h, s/iris3-6.h,
s/umips.h, s/usg5-4.h:
(SIGIO): Do not undef.
(BROKEN_SIGIO): New macro.

* s/gnu-linux.h:
(SIGPOLL, SIGURG): Do not undef.
(BROKEN_SIGPOLL, BROKEN_SIGURG): New macros.

* s/ptx4.h:
(SIGINFO): Do not undef.
(BROKEN_SIGINFO): New macros.

* s/ptx.h, s/template.h: Doc fix.

* s/aix3-1.h, s/bsd4-1.h, s/dgux.h, s/gnu-linux.h, s/hiuxmpp.h,
s/hpux.h, s/iris3-5.h, s/iris3-6.h, s/irix3-3.h, s/osf1.h, s/rtu.h,
s/sunos4-1.h, s/unipl5-0.h, s/unipl5-2.h, s/usg5-0.h, s/usg5-2-2.h,
s/usg5-2.h, s/usg5-3.h, s/xenix.h:
(open, close, read, write, INTERRUPTIBLE_OPEN,
INTERRUPTIBLE_CLOSE, INTERRUPTIBLE_IO): Remove.

* s/sol2-5.h (_LARGEFILE_SOURCE, _FILE_OFFSET_BITS): New macros.