Replaces jQuery.each loop for headers with a foreach loop.

src/ajax/xhr.js

@@ -102,9 +102,9 @@ if ( jQuery.support.ajax ) {
 
 					// Need an extra try/catch for cross domain requests in Firefox 3
 					try {
-						jQuery.each( headers, function( key, value ) {
-							xhr.setRequestHeader( key, value );
-						} );
+						for ( i in headers ) {
+							xhr.setRequestHeader( i, headers[ i ] );
+						}
 					} catch( _ ) {}
 
 					// Do send the request