added conv function from uint64 to timex_t and one minor bug fix
native: remove some warnings about undef functions

This PR implements `real_X` for `X in (fork, dup2, unlink, execve)`.
These function caused warnings while making the default example.
tests: add branch option to license checker
travis: add license checking rule
tests: add test_vtimer_msg_diff

This test sets three timers and renews them periodically, showing the
difference they accumulate.
tests: test_vtimer_msg_diff: use array for timers, change first to 1s
tests: test_vtimer_msg_diff: add some timers, change max values
tests: test_vtimer_msg_diff: Makefile s/PROJECT/APPLICATION/g
tests: test_bloom: fix PROJDEPS concurrency

Our buildtests build one project concurrently for multiple boards.
The current creation of the `PROJDEPS` for `test_bloom` might fail if

* board `A` notices that the dependency is missing and gets preempted,
* board `B` creates the dependency and gets preempted,
* board `A` starts the creation but gets preempted in the middle of the process,
* board `B` works with a half complete created file.

This PR creates the dependency in the individual `BINDIR`.
make: s/PROJDEPS/APPDEPS/

fixes https://github.com/RIOT-OS/RIOT/issues/1284
doc: improve APPDEPS example

Addresses https://github.com/RIOT-OS/RIOT/pull/1339#discussion_r14050325
make: evaluate the Git SHA only once
cpu: added low-level pwm driver impl for lpc2387
boards: added periph_conf.h for msba2 and avsextrem
drivers: some adjustments to low-level pwm driver

- adjusted doxygen and boilerplate
- changed return values for start and stop functions
board - pttu: added periph_conf.h
sys: added color module
cc110x_ng: build cc110x_spi for all boards except chronos
you can never have enough debugging in RPL
some minor fixes and debugging