Serial#Find method for Arduino, implemented in Mbed

Adoption of https://www.arduino.cc/en/Serial/Find, implemented without use of interrupts or buffers. Note that it keeps the thread busy, so if you're running this in the background, better use Serial#attach with a buffer.

History

Initial commit, tested on K64F with ESP8266 module default tip

2017-11-10, by Jan Jongboom [Fri, 10 Nov 2017 21:11:04 +0900] rev 0

Initial commit, tested on K64F with ESP8266 module