Add unlikely() to CHECK_FOR_INTERRUPTS()

Add the unlikely() branch hint macro to CHECK_FOR_INTERRUPTS().
Backpatch to REL_10_STABLE where we first started using unlikely().

Discussion: https://www.postgresql.org/message-id/flat/8692553c-7fe8-17d9-cbc1-7cddb758f4c6%40joeconway.com

src/include/miscadmin.h

@@ -98,16 +98,16 @@ extern void ProcessInterrupts(void);
 
 #define CHECK_FOR_INTERRUPTS() \
 do { \
-	if (InterruptPending) \
+	if (unlikely(InterruptPending)) \
 		ProcessInterrupts(); \
 } while(0)
 #else							/* WIN32 */
 
 #define CHECK_FOR_INTERRUPTS() \
 do { \
-	if (UNBLOCKED_SIGNAL_QUEUE()) \
+	if (unlikely(UNBLOCKED_SIGNAL_QUEUE())) \
 		pgwin32_dispatch_queued_signals(); \
-	if (InterruptPending) \
+	if (unlikely(InterruptPending)) \
 		ProcessInterrupts(); \
 } while(0)
 #endif							/* WIN32 */