Merge pull request #3615 from authmillenon/conn/feat/initial

Makefile.dep

Makefile.pseudomodules

sys/include/net/conn.h

sys/include/net/conn/ip.h

sys/include/net/conn/tcp.h

sys/include/net/conn/udp.h

sys/include/net/gnrc/conn.h

sys/net/gnrc/Makefile

sys/net/gnrc/conn/Makefile

sys/net/gnrc/conn/gnrc_conn.c

sys/net/gnrc/conn/ip/Makefile

sys/net/gnrc/conn/ip/gnrc_conn_ip.c

sys/net/gnrc/conn/udp/Makefile

sys/net/gnrc/conn/udp/gnrc_conn_udp.c

tests/conn_ip/Makefile

tests/conn_ip/ip.c

tests/conn_ip/main.c