tests: let license checker check headers, too
make: don't call mkdir -p a lot
make: use $@ and $<
make: call ranlib
make: don't invoke wildcard repeatedly
make: easier to read object targets
sys: remove lib/hashtable.c

Quoting myself:

> The code of sys/lib/hashtable.c is very badly adapted for embedded
> systems. The used primes are huge, and the limit is entirely
> unrealistic. Why do we ship this file?

In #1564 we came to the conclusion that we don't need this code.

Closes #1564.
core: introduce KERNEL_PID_FIRST and KERNEL_PID_LAST
core: let valid PIDs start with 1
all over the place: use sched_active_pid

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.
core: SCHED_PRIO_LEVELS==16 for every board

Closes #1399.

> Using a different value for SCHED_PRIO_LEVELS for 16 and 32 bit
platforms hurts portability, one thing that we heavily advertise about
RIOT. if you want to write a portable application, then you have to
assume the lower value.

This PR defaults `SCHED_PRIO_LEVELS` to 16 for every board.
make: added CPU_MODEL & TERMFLAGS to Makefile.vars

- added CPU_MODEL variable
- added TERMFLAGS variable
- fixed a little style (dots on the end of comments)
Merge pull request #1591 from haukepetersen/fix_make_vars

make: added CPU_MODEL & TERMFLAGS to Makefile.vars
board/pca10000: added make targets

- added `reset` target
- added `debug` target
- added `debug-server` target
- adjusted `flash` target
Merge pull request #1590 from haukepetersen/fix_nrf_maketargets

board/pca10000: added make targets
examples/ccn-lite-relay: remove unnecessary USEMODULE
Merge pull request #1592 from thomaseichinger/ccn-lite-relay-rtc

examples/ccn-lite-relay: remove unnecessary USEMODULE
cpu: initial import of stm32f1
boards: initial import of iot-lab_M3
at86rf231: introduce variable to keep internal driver state

The at86rf231 radio transceiver provides one IRQ (TRX_END) signaling
end of transmission or reception but no way to distinguish between
these.