doc signal handler return type

[Kevin Ryde]

Bob Friesenhahn reports that POSIX.1 allows "int" return type, so
perhaps the words below.

        * doc/autoconf.texi (Function Portability): Add notes on signal
        handler return type, as per AC_TYPE_SIGNAL.

`signal' handler
     Normally `signal' takes a handler function with a return type of
     `void', but POSIX allows it to require `int' instead.  Any actual
     `int' value returned is not used, this is only a difference in the
     function prototype demanded.

     All systems we know of in current use take `void'.  Presumably
     `int' was allowed in order to support K&R C, where of course
     `void' is not available.  `AC_TYPE_SIGNAL' (*note Particular
     Types::) can be used to establish the correct type in all cases.

autoconf.texi.signal.diff
Description: Text document