* Prevent divide by zero error causing code to crash
As per the issue at #2491, there is a divide by error issue resulting from the specification of 0 as the frequency. This does not appear to affect the AVR implementation, but it crashes on ESP8266s. I have merely removed the division if the frequency is zero, which appears to be giving the expected results (no tone), without any code crashes.
To test, simply load the toneMelody sketch included with the Arduino IDE (Examples -> 02. Digital -> toneMelody) and change the piezo to something else if you need to. On the Witty module used to test this, I could also tell by the wifi led blinking every time the code crashed as the ESP8266 immediately rebooted.
* Use noTone when frequency is zero
When a frequency of zero is given to tone(), instead call noTone() and exit. Placed after some of the initialisation stuff to ensure the pin is mapped as a output, etc. Tested as functional against a Node MCU 1.0 board and the toneMelody example sketch, using GPIO5 (pin D1).
* Errant tab in formatting
* Rest of tabs that crept in from web editor
Defaulted to tabs and 8 indent :sigh:
This includes empty stubs for most core Arduino functions.
Need to actually implement all those digital reads writes whatever.
Need to prebuild toolchains (xtensa-elf-lx106) for 3 platforms and put them on some download server.
Need to do the same with esptool.
Need to fix 0x40000 binary generation and add correct upload commands.
Maybe even implement uploads over WiFi.
