change supportsArrayBuffer check to work with Safari

Author: chmanie

dist/jspdf.debug.js

@@ -2078,7 +2078,7 @@ var jsPDF = (function(global) {
 	 * Check to see if ArrayBuffer is supported
 	 */
 	jsPDFAPI.supportsArrayBuffer = function() {
-		return typeof ArrayBuffer === 'function' && typeof Uint8Array !== 'undefined';
+		return typeof ArrayBuffer !== 'undefined' && typeof Uint8Array !== 'undefined';
 	};
 
 	/**