Add sparse array performance improvement for inArray. Thanks rwaldron, rkatic, and jdalton

src/core.js

@@ -694,7 +694,8 @@ jQuery.extend({
 			i = i ? i < 0 ? Math.max( 0, len + i ) : i : 0;
 
 			for ( ; i < len; i++ ) {
-				if ( array[ i ] === elem ) {
+				// Skip accessing in sparse arrays
+				if ( i in array && array[ i ] === elem ) {
 					return i;
 				}
 			}

test/unit/attributes.js

@@ -156,7 +156,7 @@ test("attr(Hash)", function() {
 });
 
 test("attr(String, Object)", function() {
-	expect(77);
+	expect(78);
 
 	var div = jQuery("div").attr("foo", "bar"),
 		fail = false;