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
native: override INCLUDES w/ NATIVEINCLUDES

Currrently native overrides the object file targets, because it needs
the different include paths to interact with libc and the OS.

This PR simplifies their makefiles to only override the variable
INCLUDES, instead of overriding the targets.
Extend CC2420 driver to comply with interfaces described in 'radio_driver.h'
Correction of HAL for CC2420 on concerned boards
core/msg: fix, optimize and improve

fixes:
fix race conditions by reordering dINTs
prevent null pointer dereference by adding forgotten target check
add forgotten eINTs
replace printf with DEBUG
fix debug messages

optimizations:
optimize pid access
reorder msg_send switches

improvements:
add debug statements
add missing return value to msg_send_to_self documentation
Merge pull request #1373 from Kijewski/easify-nativeincludes-usage

native: easify NATIVEINCLUDES usage
Merge pull request #1223 from rousselk/cc2420-extended-driver

CC2420: modify&extend driver to comply with API described in 'radio_driver.h'
x86: increase timeout in qemu's term

Currently `boards/qemu-i386/dist/term.py` expects QEMU to connect in
less than 5 seconds, which is plenty on any user machine. Travis CI,
which we use without paying a cent, sometimes fails to start QEMU in
this is timeframe, though.

This PR increases the timeout to one minute.
Merge pull request #1285 from LudwigOrtmann/msg_fixup

core/msg: prevent null pointer dereference
drivers/cc2420: fix logical error in cc2420_do_send function

Do the correct test in cc2420_do_send() function when analyzing
the result of cc2420_load_tx_buf()
boards/xx/driver_cc2420: fix race condition in CCA determination

Ensure that CS is active and IRQ disabled when querying CCA
on CC2420 (cc2420_get_cca() function).
Also do a little refactoring (renamed c variable into count,
and named the constant corresponding to RSSI "timeout").
make: removed shell_commands dependency
Merge pull request #1383 from rousselk/fix-cc2420-tx

Fix a design error in cc2420_do_send() function
Merge pull request #1385 from rousselk/fix-cc2420-driver-cca

Fix a nasty race condition in CCA determination on CC2420
core/msg: revert part of #1285

use m->sender_pid instead of sched_active_pid again
undoes the optimization intended by #1285
fixes uint/int warning
boards/z1: fix cc2420_txrx function in CC2420 driver HAL

When waiting for transmission (to CC2420) to be done,
we were wrongly waiting for UCBUSY bit to be set,
while one should actually wait for that bit to be cleared.
Merge pull request #1382 from Kijewski/qemu-i86-term-timeout

x86: increase timeout in qemu's term
core/msg: set m->sender_pid before it is used

fixes `msg_send_to_self` condition