Remove configure probe for sys/sockio.h.

On BSD-family systems, header <sys/sockio.h> defines socket ioctl
numbers like SIOCGIFCONF.  Only AIX is using those now, but it defines
them in <net/if.h> anyway.

Supposing some PostgreSQL hacker wants to test that AIX-only code path
on a more common development system by pretending not to have
getifaddrs().  It's enough to include <sys/ioctl.h>, at least on macOS,
FreeBSD and Linux, and we're already doing that.

configure

@@ -13761,7 +13761,7 @@ $as_echo "#define HAVE_STDBOOL_H 1" >>confdefs.h
 fi
 
 
-for ac_header in atomic.h copyfile.h execinfo.h getopt.h ifaddrs.h langinfo.h mbarrier.h netinet/tcp.h sys/epoll.h sys/event.h sys/personality.h sys/prctl.h sys/procctl.h sys/signalfd.h sys/sockio.h sys/ucred.h termios.h ucred.h
+for ac_header in atomic.h copyfile.h execinfo.h getopt.h ifaddrs.h langinfo.h mbarrier.h netinet/tcp.h sys/epoll.h sys/event.h sys/personality.h sys/prctl.h sys/procctl.h sys/signalfd.h sys/ucred.h termios.h ucred.h
 do :
   as_ac_Header=`$as_echo "ac_cv_header_$ac_header" | $as_tr_sh`
 ac_fn_c_check_header_mongrel "$LINENO" "$ac_header" "$as_ac_Header" "$ac_includes_default"

configure.ac

@@ -1457,7 +1457,6 @@ AC_CHECK_HEADERS(m4_normalize([
 	sys/prctl.h
 	sys/procctl.h
 	sys/signalfd.h
-	sys/sockio.h
 	sys/ucred.h
 	termios.h
 	ucred.h

src/backend/libpq/ifaddr.c

@@ -325,10 +325,6 @@ pg_foreach_ifaddr(PgIfAddrCallback callback, void *cb_data)
 #include <sys/ioctl.h>
 #include <net/if.h>
 
-#ifdef HAVE_SYS_SOCKIO_H
-#include <sys/sockio.h>
-#endif
-
 #if defined(SIOCGIFCONF)
 
 /*

src/include/pg_config.h.in

@@ -490,9 +490,6 @@
 /* Define to 1 if you have the <sys/signalfd.h> header file. */
 #undef HAVE_SYS_SIGNALFD_H
 
-/* Define to 1 if you have the <sys/sockio.h> header file. */
-#undef HAVE_SYS_SOCKIO_H
-
 /* Define to 1 if you have the <sys/stat.h> header file. */
 #undef HAVE_SYS_STAT_H
 

src/tools/msvc/Solution.pm

@@ -359,7 +359,6 @@ sub GenerateFiles
 		HAVE_SYS_PRCTL_H                         => undef,
 		HAVE_SYS_PROCCTL_H                       => undef,
 		HAVE_SYS_SIGNALFD_H                      => undef,
-		HAVE_SYS_SOCKIO_H                        => undef,
 		HAVE_SYS_STAT_H                          => 1,
 		HAVE_SYS_TYPES_H                         => 1,
 		HAVE_SYS_UCRED_H                         => undef,