ieee802154: introduce constant for default PAN id
make: allow tagged RIOT_VERSION
tests/unittests: merge lib-ringbuffer into core

Fixup for https://github.com/RIOT-OS/RIOT/pull/2017
Merge pull request #2157 from LudwigOrtmann/unittests-lib

tests/unittests: merge lib-ringbuffer into core
test/driver_nrf24l01p: changed default GPIOs

not all boards have GPIO_x > GPIO_7, so the new values are
safer to use.
Merge pull request #2161 from haukepetersen/fix_test_nrf24

test/driver_nrf24l01p: changed default GPIOs
tests: fixed blacklisting for UART tests

changed from explicit blacklisting to feature based approach
boards: added missing UART feature

added for:
- airfy-beacon
- arduino-mega2560
- cc2538dk
- msbiot
- openmote
- pca1000[0|5]
- spark-core
- stm32f4discovery
- yunjia-nrf51822
board/mbed_lpc1768: added UART configuration
cpu/lpc1768: added basic UART driver
vtimer: set custom msg_t.type with vtimer_set_msg

Currently, when using vtimer_set_msg the corresponding msg_t is filled
with the MSG_TIMER ("12345") type.
This approach makes it difficult to differentiate between incoming
messages via vtimer_set_msg.

In this PR I introduce another parameter for the vtimer_set_msg
function to specify a custom msg_t type.
Merge pull request #2162 from cgundogan/vtimer_set_msg_param_type

vtimer: set custom msg_t.type with vtimer_set_msg
board/mbed_lpc1768: changed binary ouput to .bin
Merge pull request #2171 from haukepetersen/fix_mbed_binfile

board/mbed_lpc1768: changed binary ouput to .bin
Merge pull request #2165 from haukepetersen/fix_test_uart

test/periph_uart_xx: switched to feature based whitelisting
board/mbed_lpc1768: added flash script
Merge pull request #2167 from haukepetersen/add_lpc1768_uart

cpu/lpc1768: added basic UART driver
Merge pull request #2172 from haukepetersen/add_mbed_makeflash

board/mbed_lpc1768: added flash script
cpu/samd21: add i2c periph implementation
make: `term` depends on `flash`

If you provide both `flash` and `term` as Make goals, then `term` needs
to wait for flash.