- This document is the result of original work by @haukepetersen and
  refinement by @miri64, @aabadie, @kaspar030, @jcarrano,
  @PeterKietzmann, @ZetaR60, and @jia200x.

drivers/saul :sys/phydat: add definitions for TVOC sensor type and PPB unit

gnrc_pktbuf_cmd: module is not a pktbuf implementation

When I introduced this pseudo-module in #9391 I did not consider, that
the way I named it, it is assumed to be an implementation of the
`gnrc_pktbuf` interface. However, it is not (it just provides the shell
command).

This PR excludes `gnrc_pktbuf_cmd` from the selection algorithm, so
that if it is the only `gnrc_pktbuf_%` module, still
`gnrc_pktbuf_static` gets selected.

cpu/nrf52: enable instruction cache

sys/random: add SHA1PRNG

sock_dns: fix typo in doc

cpu/lm4f120: remove useless periph file guard

`s/fuction/function/` ;-)

unittests: fix (some more) invisible unicode chars in Makefiles

tests/unittests, cn_cbor: remove invisible unicode char from Makefile

shell_commands: add command for packet buffer stats

I'm using something like this command for a while now for debugging
GNRC. Usually, I just patch it into the application I'm using it with,
but I think there is a benefit to also provide it to RIOT upstream
properly.

atmega_common/gpio.c: Fixes GPIO_LOW interrupt

cpu/lpc2387: Various fixes for GPIO driver

gnrc_rpl: exit early if netif_hdr is NULL in send function

examples/lorawan: use new nucleo names for BOARD_INSUFFIENT_MEMORY

Without this fix RPL might crash when the packet buffer is full.

examples/lorawan: add autonomous lorawan class A device example

gnrc_ipv6_nib: add full RFC4862 DAD support

 sys/newlib: Bugfix, add missing syscalls (only stubs)

sock_udp: allow creation with ephemeral ports

fixes the GPIO_LOW interrupt on the atmega platform.
It results from trying to shift GPIO_LOW. Since it is 0, it is not shiftable and will not be set correctly.
There were more issues with the other flanks too, as they are 0b01 or 0b00. If 0b11 was set as a flank before it would not be able to switch to any other mode anymore. Now the bits get cleared before the new flank will be written.

uncrustify: special function ISR

gnrc_rpl: remove events from the queue before memset()

pkgs/cmake: fix CFLAGS given two times

nanocoap_sock: split generic request function of from nanocoap_get

pkg/relic: Update to new upstream and remove now obsolete patches

The removed patches have been applied upstream.