ccnl: remove useless config module
ccnl: extra debug statements
shell: added RPL route shell command
drivers: fixes to the low-level GPIO driver

- fixed doxygen comments
- added GPIO_UNDEFINED value
- added return values to all functions
Merge pull request #971 from haukepetersen/periph_gpio_fix

drivers: fixes to the low-level GPIO driver
core/cpu/board: moved F_CPU define to board
Merge pull request #872 from OlegHahm/rpl_route_shell_command

sys: net: rpl: added RPL route shell command
Merge pull request #920 from haukepetersen/fcpu_to_board

core/cpu/board: moved F_CPU define to board
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`
Add readme for the hello-world example

Closes #1070.
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
Merge pull request #1072 from Kijewski/issue-1070

Add readme for the hello-world example
shell:ps: SCHEDSTATISTICS cols only if needed
make/native: remove -gc flag

Yields warning on OSX.
Uncertain why it was there in the first place.

Fixes #1125