Add script to help calculate best UART modulation value.

Details are in datasheet.
WIP AVR ISP protocol. Based on AVR910.
WIP USB host protocol.
WIP Cotex-M: Timer using Cycle Count (CYCCNT) debug register.
Enumaration of all MSP430 IRQ handlers. Was rejected - handlers belong to specific blocks.
timer_irq_dispatch_msp430.hpp.function
irq_dispatch_msp430.hpp.old
Older versions of IRQ dispatching impls.
WIP Add RTOS-style virtual timer.
WIP Dynamic pin GPIO implementation.
Example for dynapin.
WIP Buffered interrupt-driven UART.
WIP Buffered UART demo.
gpio_msp430: Assign relative port numbers.
Elaborate MSP430 gpiodyn implementation.
Elaborate BufferedUart class.
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.