added esp8266 Arduino compatibility

[nullboundary]

Hi,

Your pixels library looks great so I decided to make it compatible with the esp8266 Arduino core. So I could use it in my projects.

here is the core library if you are not familiar:
https://github.com/esp8266/Arduino

I only have an ILI9341 screen so I only changed that device file, however the changes should work if applied to the other screens. The changes work for both the sw SPI and the hw SPI.

hwSPI can run through the whole PixelsTest sketch however it does hang on the antialias drawLines grid for some reason. (SPI too slow?) If I comment that out it can make it through the rest of the sketch.

swSPI draws much faster and doesn't hang on the antialias drawLines gride. So surprisingly swSPI is better on the esp8266 then the hwSPI. Perhaps the esp8266 hwSPI core library needs more work?

If you like these changes you should submit your library to the esp8266 libraries wiki.