Port of Espruino to Pi Zero - native - no Linux

Neil, I think this is actually a pretty interesting idea! I think there are a number of options along a spectrum, actually, and I'm not sure which would end up being the most interesting:

• espruino running on linux on a PiZ
  
• espruino running on linux on a PiZ, with a kernel driver for the more time critical functions, e.g. digitalPulse, pinWatch, neopixelWrite, ...; make it easy to add functions to the kernel driver
  
• espruino running on linux on a PiZ fully in the kernel
  
• espruino running on linux on a dual-core processor (e.g. esp32?) using one core and linux on the other core
  
• espruino running on the PiZ without linux