examples: Example for dynapin.
examples: Add example of interfacing C code with PTL.

Of course, this is pretty inefficient - the idea is to wrap efficient
templated, inlinable C++ call into public, non-inlinable C function. But
if there's need to interface with legacy C code - well, that's possible.
Makefile.rules: Use C compiler to compile C sources, after all.

Required for C interoperatibility example.
mps430: Add script to help calculate best UART modulation value.

Details are in datasheet.
protocol: AVR ISP protocol. WIP.

Based on AVR910.
protocol: USB host protocol, very rough sketch WIP.
cortex-m: Timer using Cycle Count (CYCCNT) debug register.
examples: HW configs: explicitly define hardware uart object (hwuart).

Some examples require hardware UART with interrupt support, etc., so make
it obvious.
examples/uart_echo_irq.cpp: Update for PTL namespace and HW config.
circular.hpp: Mark few methods volatile for interrupt-safe operation.
buffered_uart.hpp: Buffered interrupt-driven UART.
examples: Buffered UART demo.
docs: Add data model description (including advanced topics).
virt_timer.hpp: Add RTOS-style virtual timer.
Some initial hack to support LPC800 bootrom with drivers.

Drivers are arguably ugly. The whole idea of this is to show that PTL can
wrap such ROM drivers, not to promote their usage.