tests/gnrc_ipv6_nib: Fix unused function error w/ clang/macOS

tests/gnrc_ipv6_nib_6ln: Fix error w/ clang on macOS

In the case that GNRC_IPV6_NIB_CONF_ARSM is set but
GNRC_IPV6_NIB_CONF_6LN is not, clang complains about
the function _get_l2addr_from_ipv6 never being used.
I couldn't easily figure out why this passes in Murdock,
but I'm guessing that clang is simply being smarter than
GCC. Can someone comment on whether there is a better fix
for this?

Relates to #6473

_is_reachable is only used when GNRC_IPV6_NIB_CONF_ARSM
is enabled, and as such it must be guarded so that clang
doesn't complain about a unused function in case
GNRC_IPV6_NIB_CONF_ARSM is not set

Similar to #7910
Relates to 6473

gnrc_lwmac: port to gnrc_netif2

dist: compile_test: cleanup after buildtest

[backport] Release notes of 2017.10

drivers/sx127x: Fix misc variable types and lengths

trickle: correctly reset t

tests/driver_servo/main.c: fix var len

pm_layered: make sure no conflict for pm_set_lowest exists

sys: libc: only add include path on non-native boards

Removed a comma from the Boards API reference.

We are at a point were building all of RIOT takes massive amounts of
storage. Since my machine runs full after only compiling ~20
applications (I have ~170 GB free storage if the RIOT repo is clean).

Thus the easiest solution for the compile tests is to just clean-up the
mess they made ;-).

tests/driver_isl29125/main.c: fix counter var type

tests/driver_adcxx1c: fix warning unused  argument

drivers/encx24j600/encx24j600.c : fix counter var length

Update package tiny-asn1

examples/emcute: return after printing error message

sys/can: fix building errors on native OS X

test/unittests: set pexpect timeout to 60s