sys: net: replace dev_eth with netdev2, adapt native tap driver

boards/native/Makefile.dep

boards/native/Makefile.include

cpu/native/Makefile

cpu/native/include/native_internal.h

cpu/native/include/netdev2_tap.h

cpu/native/native_cpu.c

cpu/native/netdev2_tap/Makefile

cpu/native/netdev2_tap/netdev2_tap.c

cpu/native/startup.c

cpu/native/syscalls.c

sys/auto_init/Makefile

sys/auto_init/auto_init.c

sys/auto_init/dev_eth/Makefile

sys/auto_init/dev_eth/dev_eth_autoinit.c

sys/auto_init/netif/auto_init_netdev2_tap.c

sys/include/dev_eth_autoinit.h

sys/include/net/dev_eth.h

sys/net/gnrc/link_layer/netdev_eth/Makefile

sys/net/gnrc/link_layer/netdev_eth/gnrc_netdev_eth.c