* event-top.c (async_stop_sig) [HAVE_SIGPROCMASK]: Some

* event-top.c (async_stop_sig) [HAVE_SIGPROCMASK]: Some
gratuitious whitespace changes.
[!HAVE_SIGPROCMASK]: Call sigsetmask if HAVE_SIGSETMASK is defined.
* top.c: Remove redundant logic to define HAVE_SIGSETMASK.
(sigsetmask) Don't define macro.
(stop_sig) [HAVE_SIGPROCMASK]: Add bit of code snatched from
async_stop_sig from event-top.c.
[!HAVE_SIGPROCMASK]: Call sigsetmask if HAVE_SIGSETMASK is
defined.
* configure.in (AC_CHECK_FUNCS): Put functions in alphabetical
order.  Add sigsetmask.
(AC_FUNC_VFORK, AC_FUNC_ALLOCA): Reorder such that they're in
alphabetical order.
* config/xm-aix4.h, config/alpha/xm-alphalinux.h,
config/i386/xm-cygwin.h, config/rs6000/xm-rs6000.h
(HAVE_SIGSETMASK): Remove.
* aclocal.m4, config.in, configure