Added 24 bit colour handling alphaBlend to reduce precision loss in multiple blend stages (e.g. in 2D colour gradients). Added option for alpha dither to reduce colour banding in gradients with 16 bit colours.
Get rid of compile warnings.
The library has been cleaned up as it has got a bit untidy due to the large number of small incremental changes.
4bit Sprite examples renaed to be consistent with others.
alphaBlend example moved to generic folder (alphaBlend fn was moved to TFT_eSPI class).
Added sections + explanatory comments to functions prototypes.
Temporary comments added for potential gotchas for noobs when using DMA.
spi_begin/end functions renamed to reflect functionality. Old fns retained for backwards compatibility with user setup.h files.
Added new function that sketch can call to convert raw ADC x and y
values to calibrated screen coordinates:
tft.convertRawXY(&x, &y);
Redunced required number of SPI transfers needed to read raw values.
Changed mode so PENIRQ pin is enabled so users sketch can read this
signal (if needed).
See issue #279.