Introduce set_force_quit_flag and change type of sync_quit_force_run

At the moment, handle_sigterm() in event-top.c does the following:

  sync_quit_force_run = 1;
  set_quit_flag ();

This was used several more times in a later patch in this series, so
I'm introducing (at Pedro's suggestion) a new function named
'set_force_quit_flag'.  It simply sets sync_quit_force_run and also
calls set_quit_flag().  I've revised the later patch to call
set_force_quit_flag instead.

I noticed that sync_quit_force_run is declared as an int but is being
used as a bool, so I also changed its type to bool in this commit.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=26761
Approved-By: Pedro Alves <pedro@palves.net>

gdb/defs.h

@@ -171,7 +171,10 @@ extern quit_handler_ftype *quit_handler;
 extern void default_quit_handler (void);
 
 /* Flag that function quit should call quit_force.  */
-extern volatile int sync_quit_force_run;
+extern volatile bool sync_quit_force_run;
+
+/* Set sync_quit_force_run and also call set_quit_flag().  */
+extern void set_force_quit_flag ();
 
 extern void quit (void);
 

gdb/event-top.c

@@ -1209,7 +1209,15 @@ async_sigterm_handler (gdb_client_data arg)
 }
 
 /* See defs.h.  */
-volatile int sync_quit_force_run;
+volatile bool sync_quit_force_run;
+
+/* See defs.h.  */
+void
+set_force_quit_flag ()
+{
+  sync_quit_force_run = true;
+  set_quit_flag ();
+}
 
 /* Quit GDB if SIGTERM is received.
    GDB would quit anyway, but this way it will clean up properly.  */
@@ -1218,8 +1226,7 @@ handle_sigterm (int sig)
 {
   signal (sig, handle_sigterm);
 
-  sync_quit_force_run = 1;
-  set_quit_flag ();
+  set_force_quit_flag ();
 
   mark_async_signal_handler (async_sigterm_token);
 }

gdb/utils.c

@@ -641,7 +641,7 @@ quit (void)
 {
   if (sync_quit_force_run)
     {
-      sync_quit_force_run = 0;
+      sync_quit_force_run = false;
       throw_forced_quit ("SIGTERM");
     }