gnrc_pktbuf_static.c: fix overflow in gnrc_pktbuf_realloc_data

tests:xtimer_hang: use THREAD_STACKSIZE_DEFAULT instead of literal.

tests: allow language extensions for fault_handler test in clang

This patch fixes overflow, which is caused by
(pkt->size - aligned_size). This happens if pkt->size and
new size are unaligned and the difference
between pkt->size and new size is less than four.

tests: remove vtimer tests

drivers/kw2xrf/kw2xrf.c: fix MAX_PKT_LENGTH

fixes several bugs on GNRC network stack

When ENABLE_DEBUG is 1, `out` is dereferenced unconditionally, but
`_parse_options` in `gnrc_rpl_control_messages.c` calls it with NULL.

Clarified `out` must not NULL and fixed `_parse_options`.

When `gnrc_ndp_node_next_hop_l2addr` cannot resolve L2 address, it creates a
temporary neighbor cache entry with interface `KERNEL_PID_UNDEF` (unless the
interface is already known) to send a neighbor solicitation. When another packet
directed to the same address is going to sent before receiving a neighbor
advertisement, `gnrc_sixlowpan_nd_next_hop_l2addr` gets the temporary neighbor
cache entry and calls `gnrc_ipv6_netif_get` with `KERNEL_PID_UNDEF`, resulting
get a `NULL`. We must check `NULL` before dereference it.

FYI, both `gnrc_ndp_node_next_hop_l2addr` and
`gnrc_sixlowpan_nd_next_hop_l2addr` are enabled when
`gnrc_sixlowpan_border_router_default` module is enabled with `GNRC_NETIF_NUMOF`
is greater than 1:

gnrc_sixlowpan_border_router_default
→ gnrc_ipv6_router_default
→ gnrc_ndp_router (if GNRC_NETIF_NUMOF > 1)
→ gnrc_ndp_node
→ gnrc_ndp_node_next_hop_l2addr is called from _next_hop_l2addr

gnrc_sixlowpan_border_router_default
→ gnrc_sixlowpan_nd_border_router
→ gnrc_sixlowpan_nd_router
→ gnrc_sixlowpan_nd
→ gnrc_sixlowpan_nd_next_hop_l2addr is called from _next_hop_l2addr

This patch fixes MAX_PKT_LENGTH on kw2x radio

tests: fix clang missing field error

pkg: oonf_api: move source

Without this clang complains about missing initializers.
`error: missing field 'microseconds' initializer [-Werror,-Wmissing-field-initializers]`

shell fib: recognize the default route as net prefix

shell: commands: fix selective outputs for nano specs

gnrc_ndp: fixed ND Option handling for 6LoWPAN

The forms of the Source/Target Link-layer Address option for 6LoWPAN are defined
in RFC 4944 Section 8:
https://tools.ietf.org/html/rfc4944#section-8
The address is 16 bit if length is 1, 64 bit if length is 2.

native: make use of TLSF malloc and co

tftp: fix formatting warnings/errors

periph/gpio: extend gpio API doc

periph/uart: extend uart API doc

sys: net: disable NHC

pkg: ccn-lite: pin to upstream commit

unittests: some fixes to fib_sr tests

gnrc_ndp_internal: add missing unlock when the pktbuf is full

In order to make native behave more similar to other platforms, it should also use TLSF's dynamic memory allocation if included. It will still fall back to the system's malloc implementation when building for use with valgrind, to leverage its memory leak detection mechanisms.