ng_icmpv6_echo: fix call to undefined function

drivers: Add NVRAM API

This is a simple test application for the nvram_spi driver for tests on
actual hardware.

ISL29020 fixes

Problem:

Since `i2c_read_reg` returns (signed) `int` values, the result can
be negative. However, the variable used to save the result is unsigned.

Fix:

Add and use a signed variable for return value storing.

dist: Makefile to work with IoT-LAB

drivers: added driver for PCD8544 LCD display

ng_icmpv6: Initial import

aodvv2: fix check for redundant RREQ

sys/auto_init: added mechanism for initialization of network devices

dist: add desvirt

ng_ipv6: use netapi_receive()

ipv6_nc: add iterators

ng_udp: remove unused variable

ng_sixlowpan: fixes

drivers/ng_at86rf2xx: disable debug