changed parameters form `kernel_pid_t` to `int`
board/pca1000x: added/fixed dist scripts

- pca10000: added author to debug.sh
- pca10005: added debug and reset scripts
- pca10005: fixed flash script
- pca10005: adjusted env vars in Makefile.include
Fix thread_yield by avoiding the (too) early re-enablement of IRQ,
that is: before the newly selected thread's context is totally restored
Prevent the compiler to add an unwanted prologue in thread_yield()
Fix the race condition when an interruption occured at the beginning
of thread_yield(), i.e.: just after SR(R2) was pushed but before
the rest of the suspended thread's context was pushed!
core: priority_queue: simplify inheritance
vtimer: no needless type casting

Compare https://github.com/RIOT-OS/RIOT/pull/1639#issuecomment-54713048
and following discussion.
unittests: make: Fix unittests for branch changes

Changing between branches in git typically leaves directories empty and
does not remove them. If you have different unittests in different
branches this leads to an error in building them, since the current
configuration expects a Makefile in all `tests-*` directory. This change
configures Make to search for a Makefile in `tests-*` rather than just
assuming that there is one.
Fixed comments
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
Merge pull request #1644 from Kijewski/vtimer-less-casting

vtimer: no needless type casting
Merge pull request #1639 from authmillenon/simplify_queue_inheritance

core: priority_queue: simplify inheritance
sixlowpan: ignore incoming packets if unconfigured

If there's no IPv6 address configured so far to any interface, 6lowpan
should not try to  handle incoming packets. This can easily lead to
looping packets.
sixlowpan: documented internal is_our_address()
Merge pull request #1606 from OlegHahm/sixlowpan_ignore_unconfigured

sixlowpan: ignore incoming packets if unconfigured
rpl: mute RPL

Removes all but one occurrence of printf and puts within routing (the
remaining puts is called from a debug function.
tests: don't build test/libfixmath on Travis CI

Very often the build unexplainably hangs.
Merge pull request #1648 from Kijewski/no-test-libfixmath

tests: don't build test/libfixmath on Travis CI