cpu/nrf51822: changed ISR stack size to 512 byte
cpu: adjusted IRQ stack sizes for Cortex CPUs
Merge pull request #1954 from haukepetersen/fix_cortex_irqstacksize

cpu: adjusted IRQ stack sizes for Cortex CPUs
core: remove needless test in msg.c

`thread.c` initializes a thread with an empty message queue. `cib_put()`
will `return -1` for an empty CIB, so there is no need to test if
`thread->msg_array != NULL`.
cpu/stm32f1: c++: added _kill (weak) and weak attribute for _kill_r
boards/iot-lab_M3: provided c++ feature
initial support for c++ for this cpu/board
Merge pull request #2013 from Kijewski/msg-needless-test

core: remove needless test in msg.c
Merge pull request #1985 from BytesGalore/EasyCPPMixing_stm32f4discovery_support_fix

squashed, changed comment and go.
Merge pull request #2004 from dangnhat/cpp_for_iot_lab_m3

iot-lab_m3: C++ support
Merge pull request #1932 from haukepetersen/fix_nrf_isrstacksize

cpu/nrf51822: changed ISR stack size to 512 byte
added a core implementation of FIB tables using generic addresses in an outer table structure
- the basic functions are implemented for operating FIB tables, register RPs/RRPs
  and signal RRPs when no destination is available for a next hop request
- generic addresses are implemented using a use_count to trigger if an address can be reused/overwritten
  once allocated memory will remain allocated until calling deintialisation for `generic_address`, pruning all entries
  or when an unsed entry is overwritten with a new entry of distinct size
- FIB tables are statically represented by an array of entries pointing to generic_address entries

TODO:
- handling for preference sets for colliding next hops
- test the implementation with the real network layer
- using the type field to recognize/apply compression
  - use compression, e.g. LOWPAN_IPHC

NOTE:
this is a prototype implementation it can be considered just as a proof of concept in this state
It follows strictly KISS. So, no fancy algorythms nor code hocus-pocus is applied.
[SQUASH ME] switched the implementation to a single FIB table.
            added tests for operating the FIB using the generic address structure
[SQUASH ME] added fib back to Makefile to be build
[SQUASH ME] added in/out parameter for the interface ID for `get_nexthop(...)`