removing possible invalid check

Checking for a link local address to determine if a node is on-link is
probably not a valid assumption in most wireless networks.
native: don't use RIOT read/write in UART
examples/rpl_udp: use defaulttransceiver
Added standard way to query CCA status on CC2420 transceiver (squashed)
Completed CC2420 constants documentation (DOxygen)
Clean up test_irq (fix #943)
Fixed error caused by non-inclusion of cc2420_txrx() prototype
Fixed implementation of channel_clear() function
Change year of file copyright
cpu: satisfy compiler in crash.c
Make: fix linebreaks in buildtest
Merge pull request #892 from OlegHahm/crash_noreturn

cpu: satisfy compiler in crash.c for ARM and MSP430
Fix for WSN430 1.4 driver
fixup for #710: use subfolder in bin dirs (native)

Update native Makefiles to provide changed object target paths
Fixes #989
Merge pull request #992 from LudwigOrtmann/fixup_710

fixup for #710: use subfolder in bin dirs (native)
Merge pull request #873 from OlegHahm/on_link_check

net: sixlowpan: removing possible invalid check
Fix length of fragmentation buffer in 6LoWPAN
Merge pull request #870 from authmillenon/fragbuf

sys:net:sixlowpan: Fix length of fragmentation buffer in 6LoWPAN
Merge pull request #915 from rousselk/radio-cca

Add a standard way to query CCA status on CC2420 transceiver.
Make: do not spam error messages on shallow clones

> `--always`: Show uniquely abbreviated commit object as fallback.