Setup/Loop Entry Point

[pre63]

This fixes the issue were are after a short amount of time (~9 minutes) the Blink example stops working. Issue #1.

This also fixes the usb serial not being available after upload of a juniper program.

Tested on Arduino Nano 33 BLE. Initially the led stops blinking after 9 minutes. After using the setup and loop functions which are called by the Arduino library the led blinks for over 12 hours.

My suspicion is that since the Arduino code can't determine that there was a while loop running because the code was not using the loop function the Arduino device entered a sleep mode.

In this PR

• Compiler changed to generate setup and loop functions instead of the main/while true.
• Compiler warns if the setup and loop functions are missing.
• Examples updated with setup/loop functions instead of main.

[calebh]

It is probably best to use the setup and loop functions since this matches the Arduino standard. The call to init() is no longer necessary if we use setup/loop since the default Arduino main function calls it. It looks like we were missing some initialization code and a couple of other things (see here: https://github.com/arduino/ArduinoCore-avr/blob/2f67c916f6ab6193c404eebe22efe901e0f9542d/cores/arduino/main.cpp )