port tone function to other boards

[eadmaster]

current implementation of the _tone() function won't work with boards that does not have a single pin buzzer, like the cardputer.

Temp workaround: move this constant in the platformio.ini and add a test macro in the code:

#define BUZZ_PIN 2

Better solution:
add a squarewave generator for boards that have a speaker and play the waveform with ESP8266Audio

[bmorcelli]

True...

I'll move it to platformio.ini and add a flag on "features" to fix it. Thank you!

[eadmaster]

closed via #130