Fix x11 display leak (#590)

* Call XCloseDisplay in all return paths

Add test to confirm XOpenDisplay leak is plugged

* whitespace

robot_info_test.go

@@ -43,5 +43,13 @@ func TestGetSysScale(t *testing.T) {
 	log.Println("SysScale: ", s)
 
 	f := robotgo.ScaleF()
-	log.Println("sclae: ", f)
+	log.Println("scale: ", f)
+}
+
+func TestGetTitle(t *testing.T) {
+	// just exercise the function, it used to crash with a segfault + "Maximum
+	// number of clients reached"
+	for i := 0; i < 128; i++ {
+		robotgo.GetTitle()
+	}
 }

window/pub.h

@@ -191,6 +191,7 @@ typedef struct _Bounds Bounds;
 				if (items != NULL) {
 					*items = (uint32_t) nItems;
 				}
+				XCloseDisplay(rDisplay);
 				return result;
 			}
 		}

window/window.h

@@ -104,7 +104,10 @@ bool is_valid() {
 
 	// Get the window PID property
 	void* result = GetWindowProperty(mData, WM_PID,NULL);
-	if (result == NULL) { return false; }
+	if (result == NULL) {
+		XCloseDisplay(rDisplay);
+		return false;
+	}
 
 	// Free result and return true
 	XFree(result);
@@ -405,6 +408,7 @@ MData get_active(void) {
 		if (window != 0) {
 			// Set and return the foreground window
 			result.XWin = (Window)window;
+			XCloseDisplay(rDisplay);
 			return result;
 		}
 	}
@@ -494,13 +498,13 @@ void close_window_by_Id(MData m_data){
 char* get_main_title(){
 	// Check if the window is valid
 	if (!is_valid()) { return "is_valid failed."; }
-	
+
 	return get_title_by_hand(mData);
 }
 
 char* get_title_by_pid(uintptr pid, int8_t isPid){
 	MData win = set_handle_pid(pid, isPid);
-  	return get_title_by_hand(win);
+	return get_title_by_hand(win);
 }
 
 char* named(void *result) {