Mark sigint_interrupt_enabled as sig_atomic_t

This is a continuation of 78fdb1e, where this flag is set in the psql
callback handler used for SIGINT.  This was previously a boolean but the
C standard recommends the use of sig_atomic_t.  Note that this
influences PromptInterruptContext in string.h, where the same flag is
tracked.

Author: Hayato Kuroda
Discussion: https://postgr.es/m/TYAPR01MB58669A9EC96AA3078C2CD938F5549@TYAPR01MB5866.jpnprd01.prod.outlook.com

src/bin/psql/common.c

@@ -246,7 +246,7 @@ NoticeProcessor(void *arg, const char *message)
  * On Windows, currently this does not work, so control-C is less useful
  * there.
  */
-volatile bool sigint_interrupt_enabled = false;
+volatile sig_atomic_t sigint_interrupt_enabled = false;
 
 sigjmp_buf	sigint_interrupt_jmp;
 

src/bin/psql/common.h

@@ -9,6 +9,7 @@
 #define COMMON_H
 
 #include <setjmp.h>
+#include <signal.h>
 
 #include "fe_utils/print.h"
 #include "fe_utils/psqlscan.h"
@@ -22,7 +23,7 @@ extern char *psql_get_variable(const char *varname, PsqlScanQuoteType quote,
 
 extern void NoticeProcessor(void *arg, const char *message);
 
-extern volatile bool sigint_interrupt_enabled;
+extern volatile sig_atomic_t sigint_interrupt_enabled;
 
 extern sigjmp_buf sigint_interrupt_jmp;
 

src/include/common/string.h

@@ -10,13 +10,15 @@
 #ifndef COMMON_STRING_H
 #define COMMON_STRING_H
 
+#include <signal.h>
+
 struct StringInfoData;			/* avoid including stringinfo.h here */
 
 typedef struct PromptInterruptContext
 {
 	/* To avoid including <setjmp.h> here, jmpbuf is declared "void *" */
 	void	   *jmpbuf;			/* existing longjmp buffer */
-	volatile bool *enabled;		/* flag that enables longjmp-on-interrupt */
+	volatile sig_atomic_t *enabled; /* flag that enables longjmp-on-interrupt */
 	bool		canceled;		/* indicates whether cancellation occurred */
 } PromptInterruptContext;