Switch flags tracking pending interrupts to sig_atomic_t

Those previously used bool, which should be safe on any modern
platforms, however the C standard is clear that it is better to use
sig_atomic_t for variables manipulated in signal handlers.  This commit
adds at the same time PGDLLIMPORT to ClientConnectionLost.

Author: Michael Paquier
Reviewed-by: Tom Lane, Chris Travers, Andres Freund
Discussion: https://postgr.es/m/20180925011311.GD1354@paquier.xyz

src/backend/utils/init/globals.c

@@ -27,11 +27,11 @@
 
 ProtocolVersion FrontendProtocol;
 
-volatile bool InterruptPending = false;
-volatile bool QueryCancelPending = false;
-volatile bool ProcDiePending = false;
-volatile bool ClientConnectionLost = false;
-volatile bool IdleInTransactionSessionTimeoutPending = false;
+volatile sig_atomic_t InterruptPending = false;
+volatile sig_atomic_t QueryCancelPending = false;
+volatile sig_atomic_t ProcDiePending = false;
+volatile sig_atomic_t ClientConnectionLost = false;
+volatile sig_atomic_t IdleInTransactionSessionTimeoutPending = false;
 volatile sig_atomic_t ConfigReloadPending = false;
 volatile uint32 InterruptHoldoffCount = 0;
 volatile uint32 QueryCancelHoldoffCount = 0;

src/include/miscadmin.h

@@ -77,13 +77,13 @@
 
 /* in globals.c */
 /* these are marked volatile because they are set by signal handlers: */
-extern PGDLLIMPORT volatile bool InterruptPending;
-extern PGDLLIMPORT volatile bool QueryCancelPending;
-extern PGDLLIMPORT volatile bool ProcDiePending;
-extern PGDLLIMPORT volatile bool IdleInTransactionSessionTimeoutPending;
+extern PGDLLIMPORT volatile sig_atomic_t InterruptPending;
+extern PGDLLIMPORT volatile sig_atomic_t QueryCancelPending;
+extern PGDLLIMPORT volatile sig_atomic_t ProcDiePending;
+extern PGDLLIMPORT volatile sig_atomic_t IdleInTransactionSessionTimeoutPending;
 extern PGDLLIMPORT volatile sig_atomic_t ConfigReloadPending;
 
-extern volatile bool ClientConnectionLost;
+extern PGDLLIMPORT volatile sig_atomic_t ClientConnectionLost;
 
 /* these are marked volatile because they are examined by signal handlers: */
 extern PGDLLIMPORT volatile uint32 InterruptHoldoffCount;