(shutdown): Check for `shutdown' function.

configure.in

@@ -1500,7 +1500,7 @@ AC_CHECK_FUNCS(gettimeofday gethostname getdomainname dup2 \
 rename closedir mkdir rmdir sysinfo \
 random lrand48 bcopy bcmp logb frexp fmod rint cbrt ftime res_init setsid \
 strerror fpathconf select mktime euidaccess getpagesize tzset setlocale \
-utimes setrlimit setpgid getcwd)
+utimes setrlimit setpgid getcwd shutdown)
 
 # Check this now, so that we will NOT find the above functions in ncurses.
 # That is because we have not set up to link ncurses in lib-src.