ccnl: remove useless config module
ccnl: extra debug statements
ccnl: remove type warning
added `pthread_cond.h` to `pthread.h`
adjusted `test_pthread_condition_variable\main.c` includes reflecting the above change
Merge pull request #1117 from BytesGalore/add_missing_pthread_cv_header

sys:posix:pthread added missing `pthread_cond.h` to `pthread.h`
core/cpu: put __builtin_unreachable() into one place
Merge pull request #1114 from Kijewski/add_UNREACHABLE

core/cpu: put __builtin_unreachable() into one place
Merge pull request #1084 from mehlis/ccnl-debug

ccnl: extra debug statements
Merge pull request #1081 from mehlis/ccnl-config-remove

ccnl: remove unused config module
Merge pull request #1116 from Kijewski/ccnl-warnings

ccnl: remove type warning
added NORETURN to `sched_task_exit()`
added NORETURN to `cpu_switch_context_exit()`
added NORETURN to `sched_task_exit()`
removed the `extern sched_task_exit();` and added the according header
added right signature for first parameter of `thread_stack_init()`
added `UNREACHABLE();` macro to `cpu/lpc1768/atom.c` and `cpu/msp430-common/cpu.c`