Make the difflib code ES5 strict mode-compliant

Author: Alexander Pavlov

difflib.js

@@ -28,9 +28,9 @@ ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF S
 DAMAGE.
 ***/
 /* Author: Chas Emerick <[email protected]> */
-__whitespace = {" ":true, "\t":true, "\n":true, "\f":true, "\r":true};
+var __whitespace = {" ":true, "\t":true, "\n":true, "\f":true, "\r":true};
 
-difflib = {
+var difflib = {
 	defaultJunkFunction: function (c) {
 		return __whitespace.hasOwnProperty(c);
 	},