CSS: Don't name the anonymous swap function

IE8 doesn't like named anonymous expressions. Not naming the function
expression reduces the gzipped size by 5 bytes.

In ECMAScript 2015 the function will get the name inferred from the
variable name (here: swap) anyway.

(cherry-picked from e847574fc7)

Refs 02a9d9f94b

src/css/var/swap.js

@@ -1,7 +1,7 @@
 define(function() {
 
 // A method for quickly swapping in/out CSS properties to get correct calculations.
-return function swap( elem, options, callback, args ) {
+return function( elem, options, callback, args ) {
 	var ret, name,
 		old = {};