Make: do not spam error messages on shallow clones

> `--always`: Show uniquely abbreviated commit object as fallback.
Add the ability to send a message to the current thread's message queue
(without raising an error)
ccnl: LRU is the replacement strategy, rename variable to express this
native: optionally exit() after last thread has ended

Used when compiled with NATIVE_AUTO_EXIT defined.
Merge pull request #972 from kaspar030/native_exit_after_last_task_v2

Make native exit after last thread has ended
Merge pull request #1003 from mehlis/ccnl-lru

ccnl: LRU is the replacement strategy, rename variable to express this
Merge pull request #990 from Kijewski/allow-shallow-clone

Make: do not spam error messages on shallow clones
Merge pull request #970 from rousselk/send_msg_intra_thread

core: Add the ability to send a message to the current thread's message queue
Asks Git to ignore IDE-related (TI CCS) files
Initial version of the Zolertia Z1 port for RIOT OS
Add a "slow mode" option for UART (more robust, but really slow)
Implement cc2420_get_cca() function
Fix a typo that provokes many unjustified "cc2420 unexpected IFG" alerts to occur.
Updated the Makefile.include file for Zolertia Z1
(adaptation to build system changes)
CoSenS port for RIOT
Add ACK-response management (still buggy)