samr21: implemented transceiver via spi, gpio changes
exclude ``ipv6_iface_set_routing_provider()`` from ``#ifdef MODULE_RPL`` so that other routing protocols can use it too.
Merge pull request #1997 from Troels51/samr21-transceiver-port

samr21: implemention of transceiver via spi
add parentheses to ENABLE_DEBUG in CBOR_NO_PRINT
Merge pull request #2208 from Lotterleben/cbor_add_define_parentheses

add parentheses to ENABLE_DEBUG in CBOR_NO_PRINT
Make hwtimer_spin() work even with interrupts disabled
by using only 16 significative bits on MSP430 hardware timers
Reduce variable scope in init function
fix typos in ip.h, mac.h, ndp.h and types.h
Merge pull request #2210 from Lotterleben/fix_sixlowpan_typos

fix typos in ip.h, mac.h, ndp.h and types.h
samr21: implemented 32 bit hwtimer
drivers/srf08: initial import of the updated ultrasonic driver
Merge pull request #2179 from PeterKietzmann/adapt_srf08_ultrasonic_driver

drivers/srf08: improved and adapted ultrasonic ranger driver to general i2c interface
Merge pull request #1998 from Troels51/samr21-hwtimer-fix

samr21: 32 hwtimer
Merge pull request #2212 from Lotterleben/fix_ipv6_iface_set_routing_provider

exclude ``ipv6_iface_set_routing_provider()`` from ``#ifdef MODULE_RPL``...
Merge pull request #1619 from rousselk/msp430-hwtimer-16bit

Only use 16 significative bits for MSP430 hwtimers
core: introduce `msg_sent_by_int()`

msg_send_int() sets `m->sender_pid = target_pid`. This was used to flag a
message as having been sent by an ISR.

This PR introduces a static inline function `msg_sent_by_int()` and a
specific define for this purpose.
tests: remove do-while(0) blocks for netdev tests or comment on them
Merge pull request #2154 from authmillenon/tests/cq/remove-do-while-0

tests: remove do-while(0) blocks for netdev tests or comment on them
Robust use of TimerA for 'hwtimer' module
Use TimerB for 'hwtimer' module implementation