dist/tools/sniffer: Fix usec calculation

drivers: periph: add generic spi fallbacks

This module contains shared functions for periph implementations.

gnrc: Fix #3597 (multi-hop ping)

native: unify and simplify usage of tapsetup script

core: remove needless thread creation checks in kernel_init

board: limifrog-v1 initial commit

drivers: renamed further remaining *NG_* macros

cpu/stm32f1: simplified pin initialization in periph drivers

net/ng_pktbuf: added IOVEC export function

sys/shell/shell.c: command not found in one line

ndp: missing initialization

native: fixes for removal of nativenet

make: enable assert only if DEVELHELP is set

arduino_mega2560: correct uart prototypes

Test hwtimer wo sleep