core: move NTOHL and friends into byteorder.h
sys: use byteorder.h in cbor.c
core: allow inclusion of byteorder.h in C++ code
core: sys: move ringbuffer to core
Merge pull request #2017 from kaspar030/move_ringbuffer_to_core

Move ringbuffer to core
native: add random syscalls
native: add random peripheral implementation
tests/periph_random: fix warnings, conventions
c++: `s/restrict/__restrict/`

`restrict` is not a keyword in C++, but `__restrict` is understood by
GCC-ish compilers.
Merge pull request #1984 from Kijewski/net_help-is-odd

core: move NTOHL and friends into byteorder.h
Merge pull request #2041 from LudwigOrtmann/native-random

native: peripheral random interface
Merge pull request #2042 from Kijewski/restrict

c++: `s/restrict/__restrict/`