Refactor debug and vmstop request interface

Instead of fiddling with debug_requested and vmstop_requested directly,
introduce qemu_system_debug_request and turn qemu_system_vmstop_request
into a public interface. This aligns those services with exiting ones in
vl.c.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/cpus.c b/cpus.c
index ca1f01d..97a6d4f 100644
--- a/cpus.c
+++ b/cpus.c
@@ -168,8 +168,7 @@
 static void cpu_debug_handler(CPUState *env)
 {
     gdb_set_stop_cpu(env);
-    debug_requested = VMSTOP_DEBUG;
-    vm_stop(VMSTOP_DEBUG);
+    qemu_system_debug_request();
 }
 
 #ifdef CONFIG_LINUX
@@ -990,12 +989,6 @@
     qemu_event_increment();
 }
 
-static void qemu_system_vmstop_request(int reason)
-{
-    vmstop_requested = reason;
-    qemu_notify_event();
-}
-
 void cpu_stop_current(void)
 {
     if (cpu_single_env) {