vtimer: fix callback usage

There is no need to test the "handler" set in the vtimer struct, and
have some code executed then. We just can make the code to execute the
handler. To lengthy `if else if`, just a call.
ccnl: fixed commenting style
ccnl: eliminated empty translation unit warning
Reset the SAM3X8E before flashing
so as to avoid some hangups in the flashing process
Merge pull request #1034 from Kijewski/vtimer-callbacks

vtimer: fix callback usage
make: rename VERSION into RIOT_VERSION

Building MSP boards gives an error, because `VERSION` is somewhere
defined in their toolchain as an integer.

This PR renames `VERSION` into `RIOT_VERSION`, because that's what it
is.
Merge pull request #1400 from Kijewski/riot-version

make: rename VERSION into RIOT_VERSION
Merge pull request #1362 from OlegHahm/ccnl_eliminate_warning

CCN_lite eliminate warning
Update CONTRIBUTING.md

Add comment about labels, hint at Development Procedures.
core/sched: clean up

- remove stray spaces
- remove TODOs:
    - MODULE_HWTIMER is not a module anymore
    - checking for NULL is necessary, at least without API changes:
      `sched_task_exit` sets `sched_active_thread` to `NULL`, then exits,
      afterwards `cpu_switch_context_exit` calls `sched_run`
core/sched: fix pid/tcb & refactor SCHEDSTATISTICS

pid and tcb_t were compared instead of pid and pid

SCHEDSTATISTICS:
- reduce hwtimer_now calls
- dont use thread_last_pid anymore
- increase readability
core/sched: remove MODULE_NSS helpers (API CHANGE)

remove thread_getlastpid and last_pid from the API, it is unused
cpu/lpc2387: fix unused parameter warning

mark 'mode' as unused in pwm_init
Merge pull request #1405 from LudwigOrtmann/pwm_fixup

cpu/lpc2387: fix unused parameter warning
sys/vtimer: spin on short duration in vtimer_sleep

closes #571
native: remove stale TODOs and blank line

The values are quite OK.
Merge pull request #1376 from LudwigOrtmann/sched_fixup

core/sched fixup and optimize
sys/transcevier: fix more loop integers
native: enable reboot with tap

partially fixes #787
Merge pull request #1408 from LudwigOrtmann/native-cleaning

native: remove stale TODOs and blank line