ILI9341 Performance Improvements

@Gordon - Further to my reply above I have noticed an issue with 1v72 (it may also happen with 1v71, I haven't had a chance to try). Its regarding the RTC after a hard reset.

Power up Espruino and try this code (it should take 3 and a bit seconds):

function test(){
     for (var i=0;i<10000;i++){
        var j = new Array(10000);
        j.fill(0xFF);
      }
}
var t = getTime();
test();
console.log(getTime()-t);

Now disconnect IDE, hard reset & run again - zero duration!

(I hope the code above has no syntax errors, I cant run it just at present)