dist/tools: add cppcheck script

enables easy linting of the whole tree or just one branches changes against
another
SQUASHME: file(line) -> file:line

Addresses https://github.com/RIOT-OS/RIOT/pull/1604#discussion_r16936195
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
tests: hwtimer shorten wait period

A sub-two-second period is needed for 16 bit timers.
tests/hwtimer: add self as author
Merge pull request #1643 from LudwigOrtmann/tests-hwtimer-shorten

tests: hwtimer shorten wait period
drivers: Provide basic interface for all network devices
[SQUASH ME] rename net_dev to netdev
drivers: Make general IEEE 802.15.4 driver part of net_dev
[SQUASH ME] apply netdev rename to 802.15.4 drivers
nativenet: Apply coding conventions
nativenet: Supply net_dev_t support for nativenet
[SQUASH ME] apply netdev rename to nativenet port
net_dev: Provide some default values dependent on module selection
[SQUASH ME] apply rename of netdev to netdev/default.h