Remove unneeded volatile qualifiers from postmaster.c.

Several flags were marked volatile and in some cases used sig_atomic_t
because they were accessed from signal handlers.  After commit 7389aad6,
we can just use unqualified bool.

Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/CA%2BhUKGLMoeZNZY6gYdLUQmuoW_a8bKyLvtuZkd_zHcGVOfDzBA%40mail.gmail.com

src/backend/postmaster/postmaster.c

@@ -359,17 +359,17 @@ bool		ClientAuthInProgress = false;	/* T during new-client
 bool		redirection_done = false;	/* stderr redirected for syslogger? */
 
 /* received START_AUTOVAC_LAUNCHER signal */
-static volatile sig_atomic_t start_autovac_launcher = false;
+static bool start_autovac_launcher = false;
 
 /* the launcher needs to be signaled to communicate some condition */
-static volatile bool avlauncher_needs_signal = false;
+static bool avlauncher_needs_signal = false;
 
 /* received START_WALRECEIVER signal */
-static volatile sig_atomic_t WalReceiverRequested = false;
+static bool WalReceiverRequested = false;
 
 /* set when there's a worker that needs to be started up */
-static volatile bool StartWorkerNeeded = true;
+static bool StartWorkerNeeded = true;
-static volatile bool HaveCrashedWorker = false;
+static bool HaveCrashedWorker = false;
 
 /* set when signals arrive */
 static volatile sig_atomic_t pending_pm_pmsignal;