ESP8266, ESP32 support

[source-creator]

It would be great to get support for these chips please.

\Arduino\libraries\DirectIO/ports.h:31:20: fatal error: avr/io.h: No such file or directory
#include <avr/io.h>

[mmarchetti]

#17 should help with this, but I don't have a board to test on. If you are able to give the nonavr branch a try, I would appreciate any feedback.

[mmarchetti]

There is fallback (non-accelerated) support in #17.