Revert fix for multi-clicks in Tracker

Reverts part of 8d0464e.
That fix resulted in menus collapsing as soon as the mouse is moved.

Reverting this part fixes this, at the cost of double-clicks not working
in Tracker. Until fixed, this is acceptable, because you can just hit
ENTER to open a selected file. And ALT+CTRL+H hide a window, same as a
double-click on a window tab.

Fixes #3
Reopens #1

Author: humdingerb

src/AboutHelpWin.cpp

@@ -263,6 +263,10 @@ KeyCursorDevice::ProcessMessage(int32 what, int32 data)
 
 		case BUTTON_UP:
 		{
+			fClickedButton = 0;
+			fLastClick = 0;
+			fClickCount = 0;
+
 			BMessage* event = new BMessage(B_MOUSE_UP);
 			event->AddInt64("when", now);
 			event->AddInt32("x", 0);