[SQUASH ME] netapi: Add option type to get registered threads
[SQUASH ME] basic_mac: adapt for registry getter
[SQUASH ME] apply hold/release mechanism on whole range
[SQUASH ME] make pktbuf_realloc thread-safe with release/hold mechanism
[SQUASH ME] netapi: Update license header
[SQUASH ME] basic_mac: Update license header
[SQUASH ME] unittests: tests-basic_mac: Update license header
[SQUASH ME] tests: nativenet_netapi: Update license header
[SQUASH ME] tests: netdev: Add license header
Merge branch 'net-dev-base' into network-layer-interface
Merge branch 'packetbuf2' into uart_net
Merge branch 'network-layer-interface' into uart_net