Split WaitEventSet functions to separate source file

latch.c now only contains the Latch related functions, which build on
the WaitEventSet abstraction. Most of the platform-dependent stuff is
now in waiteventset.c.

Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://www.postgresql.org/message-id/8a507fb6-df28-49d3-81a5-ede180d7f0fb@iki.fi

Author: hlinnaka

src/backend/libpq/pqsignal.c

@@ -42,7 +42,7 @@ pqinitmask(void)
 {
 	sigemptyset(&UnBlockSig);
 
-	/* Note: InitializeLatchSupport() modifies UnBlockSig. */
+	/* Note: InitializeWaitEventSupport() modifies UnBlockSig. */
 
 	/* First set all signals, then clear some. */
 	sigfillset(&BlockSig);

src/backend/postmaster/postmaster.c

@@ -548,7 +548,7 @@ PostmasterMain(int argc, char *argv[])
 	pqsignal(SIGCHLD, handle_pm_child_exit_signal);
 
 	/* This may configure SIGURG, depending on platform. */
-	InitializeLatchSupport();
+	InitializeWaitEventSupport();
 	InitProcessLocalLatch();
 
 	/*

src/backend/storage/ipc/Makefile

@@ -25,6 +25,7 @@ OBJS = \
 	signalfuncs.o \
 	sinval.o \
 	sinvaladt.o \
-	standby.o
+	standby.o \
+	waiteventset.o
 
 include $(top_srcdir)/src/backend/common.mk