xW: improve beeping

This adds yet another build dependency,
but it's better than the alternatives of handling it in code.

xW/xW.cpp

@@ -165,6 +165,14 @@ window_get_text(HWND hWnd)
 	return buffer;
 }
 
+static void
+beep()
+{
+	if (!PlaySound(MAKEINTRESOURCE(IDR_BEEP),
+			GetModuleHandle(NULL), SND_ASYNC | SND_RESOURCE))
+		Beep(800, 100);
+}
+
 // --- Networking --------------------------------------------------------------
 
 static bool
@@ -785,8 +793,7 @@ relay_process_buffer_line(Buffer &b, Relay::EventData_BufferLine &m)
 
 	if (line->is_highlight || (!visible && !line->is_unimportant &&
 		b.kind == Relay::BufferKind::PRIVATE_MESSAGE)) {
-		// TODO(p): Avoid the PC speaker, which is also unreliable.
-		Beep(800, 100);
+		beep();
 
 		if (!visible) {
 			b.highlighted = true;
@@ -1261,9 +1268,8 @@ input_complete(const InputStamp &state, const std::wstring &error,
 		SendMessage(g.hwndInput, EM_REPLACESEL, TRUE, (LPARAM) insert.c_str());
 	}
 
-	// TODO(p): Avoid the PC speaker, which is also unreliable.
 	if (response->completions.size() != 1)
-		Beep(800, 100);
+		beep();
 
 	// TODO(p): Show all completion options.
 }