dist/tools: add cppcheck script

enables easy linting of the whole tree or just one branches changes against
another
tests: improve calculation in hwtimer_wait

Kudos to @Kijewski
SQUASHME: file(line) -> file:line

Addresses https://github.com/RIOT-OS/RIOT/pull/1604#discussion_r16936195
iot-lab_M3: extend debug target for iot-lab_M3
SQUASHME: kill openocd by PID
sys: vtimer: add license header
Merge pull request #1634 from kaspar030/vtimer-license

sys: vtimer: add license header
Merge pull request #1628 from LudwigOrtmann/hwtimer_wait_fixup_2

tests: improve calculation in hwtimer_wait
native: add support for Linux on ARM
Merge pull request #1627 from LudwigOrtmann/native-arm

native: add support for ARM (Linux)
Merge pull request #1629 from thomaseichinger/iot-lab_debugger++

iot-lab_M3: extend debug target for iot-lab_M3
core: priority_queue: simplify inheritance
SQUASHME: add documentation
cpu: atmega: doxygen: blacklist upstream headers
Merge pull request #1642 from N8Fear/avr-libc-fix-doxygen

cpu: atmega: doxygen: blacklist upstream headers
SQUASHME: undo accidental commit of timex.h
SQUASHME: tool -> tools path typo
Merge pull request #1604 from LudwigOrtmann/cppcheck-script

dist/tools: add cppcheck script
vtimer: no needless type casting

Compare https://github.com/RIOT-OS/RIOT/pull/1639#issuecomment-54713048
and following discussion.
tests: hwtimer shorten wait period

A sub-two-second period is needed for 16 bit timers.