Add kqueue(2) support to the WaitEventSet API.

Use kevent(2) to wait for events on the BSD family of operating
systems and macOS.  This is similar to the epoll(2) support added
for Linux by commit 98a64d0b.

Author: Thomas Munro
Reviewed-by: Andres Freund, Marko Tiikkaja, Tom Lane
Tested-by: Mateusz Guzik, Matteo Beccati, Keith Fiske, Heikki Linnakangas, Michael Paquier, Peter Eisentraut, Rui DeSousa, Tom Lane, Mark Wong
Discussion: https://postgr.es/m/CAEepm%3D37oF84-iXDTQ9MrGjENwVGds%2B5zTr38ca73kWR7ez_tA%40mail.gmail.com

configure

@@ -12760,7 +12760,7 @@ $as_echo "#define HAVE_STDBOOL_H 1" >>confdefs.h
 fi
 
 
-for ac_header in atomic.h copyfile.h execinfo.h fp_class.h getopt.h ieeefp.h ifaddrs.h langinfo.h mbarrier.h poll.h sys/epoll.h sys/ipc.h sys/prctl.h sys/procctl.h sys/pstat.h sys/resource.h sys/select.h sys/sem.h sys/shm.h sys/sockio.h sys/tas.h sys/un.h termios.h ucred.h utime.h wchar.h wctype.h
+for ac_header in atomic.h copyfile.h execinfo.h fp_class.h getopt.h ieeefp.h ifaddrs.h langinfo.h mbarrier.h poll.h sys/epoll.h sys/event.h sys/ipc.h sys/prctl.h sys/procctl.h sys/pstat.h sys/resource.h sys/select.h sys/sem.h sys/shm.h sys/sockio.h sys/tas.h sys/un.h termios.h ucred.h utime.h wchar.h wctype.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" "$ac_includes_default"
@@ -14996,7 +14996,7 @@ fi
 LIBS_including_readline="$LIBS"
 LIBS=`echo "$LIBS" | sed -e 's/-ledit//g' -e 's/-lreadline//g'`
 
-for ac_func in backtrace_symbols cbrt clock_gettime copyfile fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memset_s memmove poll posix_fallocate ppoll pstat pthread_is_threaded_np readlink setproctitle setproctitle_fast setsid shm_open strchrnul strsignal symlink sync_file_range uselocale utime utimes wcstombs_l
+for ac_func in backtrace_symbols cbrt clock_gettime copyfile fdatasync getifaddrs getpeerucred getrlimit kqueue mbstowcs_l memset_s memmove poll posix_fallocate ppoll pstat pthread_is_threaded_np readlink setproctitle setproctitle_fast setsid shm_open strchrnul strsignal symlink sync_file_range uselocale utime utimes wcstombs_l
 do :
   as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
 ac_fn_c_check_func "$LINENO" "$ac_func" "$as_ac_var"

configure.in

@@ -1288,6 +1288,7 @@ AC_CHECK_HEADERS(m4_normalize([
 	mbarrier.h
 	poll.h
 	sys/epoll.h
+	sys/event.h
 	sys/ipc.h
 	sys/prctl.h
 	sys/procctl.h
@@ -1628,6 +1629,7 @@ AC_CHECK_FUNCS(m4_normalize([
 	getifaddrs
 	getpeerucred
 	getrlimit
+	kqueue
 	mbstowcs_l
 	memset_s
 	memmove

src/include/pg_config.h.in

@@ -331,6 +331,9 @@
 /* Define to 1 if __builtin_constant_p(x) implies "i"(x) acceptance. */
 #undef HAVE_I_CONSTRAINT__BUILTIN_CONSTANT_P
 
+/* Define to 1 if you have the `kqueue' function. */
+#undef HAVE_KQUEUE
+
 /* Define to 1 if you have the <langinfo.h> header file. */
 #undef HAVE_LANGINFO_H
 
@@ -614,6 +617,9 @@
 /* Define to 1 if you have the <sys/epoll.h> header file. */
 #undef HAVE_SYS_EPOLL_H
 
+/* Define to 1 if you have the <sys/event.h> header file. */
+#undef HAVE_SYS_EVENT_H
+
 /* Define to 1 if you have the <sys/ipc.h> header file. */
 #undef HAVE_SYS_IPC_H
 

src/tools/msvc/Solution.pm

@@ -281,6 +281,7 @@ sub GenerateFiles
 		HAVE_IPV6                                   => 1,
 		HAVE_ISINF                                  => 1,
 		HAVE_I_CONSTRAINT__BUILTIN_CONSTANT_P       => undef,
+		HAVE_KQUEUE                                 => undef,
 		HAVE_LANGINFO_H                             => undef,
 		HAVE_LDAP_H                                 => undef,
 		HAVE_LDAP_INITIALIZE                        => undef,
@@ -374,6 +375,7 @@ sub GenerateFiles
 		HAVE_SYMLINK                             => 1,
 		HAVE_SYSLOG                              => undef,
 		HAVE_SYS_EPOLL_H                         => undef,
+		HAVE_SYS_EVENT_H                         => undef,
 		HAVE_SYS_IPC_H                           => undef,
 		HAVE_SYS_PRCTL_H                         => undef,
 		HAVE_SYS_PROCCTL_H                       => undef,