Update for irq handler name refactor.
Update for latest IPin refactors.
Update for latest Delay refactors.
Add initial (mostly dummy) support for EFM32.
Refactor, implement delay_since() in terms of expired().
Make register access functions common.
Add bitfield accessors.
Allow to specify clock divider for freerun().
Andd %ld, %lx for printf().
Refactor to let switch to non-default LED easier.
Add Port 3.
Add signed and unsigned decimal prints.
Case long long calcs to uint32_t, fixes ambiguity with timer delay.
Add toggle method to Signals.
Double-include protection.
Add support for arbitrary sleep intervals (now accepts interval duration).
Update for Sleep refactors.
Make inline constexpr delay function static.

This way, non-inlined version won't be generate by compiler (will be
automagically garbage-collected).
uart_printf example.
EFM32 make rules, requir libefm32.