fixed global variables introduced in for loop with missing var-keywor…

…d (detected via QUnit's no ?noglobals)

src/selector.js

@@ -551,7 +551,7 @@ var Expr = Sizzle.selectors = {
 			} else if ( name === "not" ) {
 				var not = match[3];
 
-				for ( i = 0, l = not.length; i < l; i++ ) {
+				for ( var i = 0, l = not.length; i < l; i++ ) {
 					if ( not[i] === elem ) {
 						return false;
 					}