ILI9341 Performance Improvements

I guess it's possible that Espruino struggles to keep the higher speed SPI fully loaded with data. There's an issue open for adding DMA (mainly for non-glitchy neopixels while getting WiFi data), and I just updated it to mention this: https://github.com/espruino/Espruino/issues/1212

I can't promise when I'll have time to do something about it though. At the moment I'm not sure what to suggest - however with the WiFi's extra RAM you could use the paletted version and:

• tweak it to use bigger RAM buffers
  
• Use Graphics.getModified to get the modified area, then drawImage to draw it into a new Graphics instance of the right size and write just that instance to the screen.
  
  

While it would add some delay to the output, it would provide a much smoother, less glitchy update - especially for button presses.