- enabled power for uart and timer
- outsourced timer config values to periph_conf.h
- made linkerscript better readable
- adjusted default stack-sizes
- let RED_LED blink on hard_fault
In many places we needlessly use `sched_active_thread->pid` whilst we
already have `sched_active_pid` with the same value, and one less
indirection.
`thread_getpid()` is made `static inline` so that there is no penalty in
using this function over accessing `sched_active_pid` directly.
