ieee802154: introduce constant for default PAN id
make: allow tagged RIOT_VERSION
cpu: msp430: renamed msp430x16x to msp430fxyz
cpu: lpc2387: integrated lpc_common into lpc2387

Rationale 1: The common part made only sense for (some) NXP ARM7 MCUs,
but was misleading for MCUs like the LPC1768.

Rationale 2: The common part was only used by one specific MCU
implementation - no need to outsource it.
doc: fix doxygen group for cc2538 memory map
sys: rename lib to hash_string

That was the onyl remaining module in this folder.
tests/unittests: merge lib-ringbuffer into core

Fixup for https://github.com/RIOT-OS/RIOT/pull/2017
Merge pull request #2151 from OlegHahm/lib_hash_string

sys: rename lib to hash_string
Merge pull request #2118 from OlegHahm/simplify_cpu_folder_structure

cpu: simplify folder structure
doc: fix drivers/srf02 documentation
doc: fix drivers/srf08 documentation
Merge pull request #2160 from PeterKietzmann/fix_srf_ultrasonic_doxy_warnings

doc: doxygen fix srf02/srf08 ultrasonic warnings
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.