shell: added RPL route shell command
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
Changed RIOT/Makefile.include and boards/native/Makefile.include to compile C and C++ files.
Added another_c_cpp_mix and cpp_mix to examples folder.
address comment by @LudwigOrtmann - removed trailing space in RIOT/Makefile.include
address comment by @LudwigOrtmann - leave CXXUWFLAGS and CXXEXFLAGS empty in boards/native/Makefile.include
Added CXXEXFLAGS to another_c_cpp_mix to Makefile.include
added `missing.(h|c)` containing last missing pthread functions/defines/types
added `pthread_cond.h` `missing.h` to `pthread.h`
made includes in `pthread.h` `extern "C" if using c++`

added `bits/siginfo.h`
added `sched_yield()`
added initializers for PTHREAD_MUTEX and PTHREAD_COND
removed bits/pthread_types.h