Fix #8732. Change feature detect for focusin event support, so IE9 won't have duplicate events.

src/event.js

@@ -850,7 +850,7 @@ function trigger( type, elem, args ) {
 }
 
 // Create "bubbling" focus and blur events
-if ( document.addEventListener ) {
+if ( !jQuery.support.focusinBubbles ) {
 	jQuery.each({ focus: "focusin", blur: "focusout" }, function( orig, fix ) {
 	
 		// Attach a single capturing handler while someone wants focusin/focusout

src/support.js

@@ -226,6 +226,7 @@
 
 	jQuery.support.submitBubbles = eventSupported("submit");
 	jQuery.support.changeBubbles = eventSupported("change");
+	jQuery.support.focusinBubbles = document.attachEvent && eventSupported("focusin");
 
 	// release memory in IE
 	div = all = a = null;