fix signal handler on win32

The signal handler thread on win32 did listen to 4 HANDLEs,
of which only 3 were initialized.
The result was 1 thread eating 100% cpu.
This commit reduces the HANDLE array storage.

Signed-off-by: Kurt Van Dijck <dev.kurt@vandijck-laurijssen.be>

src/signals.c

@@ -105,7 +105,7 @@ void handle_sigusr2(int signal)
 DWORD WINAPI SigThreadProc(void* data)
 {
 	TCHAR evt_name[MAX_PATH];
-	static HANDLE evt[4];
+	static HANDLE evt[3];
 	int pid = GetCurrentProcessId();
 
 	sprintf_s(evt_name, MAX_PATH, "mosq%d_shutdown", pid);