`sock_util` includes the `arpa/inet.h` header so it has `posix` as a
dependency to include the `sys/posix/include` include path.

drivers/at: at out-of-band data support for at commands parser

tests: cpu_efm32_features: add test application

Add SRAM based PRNG seeder

tests/monocypher: Increase stack space

tools: add mosquitto.rsmb MQTT-SN broker

Improving TinyDTLS package and dtls-echo example

Due to all the changes, this is basically a new version for this
example. The main benefit is the use of sock_udp but also the client
side is now more robust and reliable.

The parameters required for the PSK and ECC (e.g. keys) modes are moved
to an unique header.

The integration of TinyDTLS for RIOT has been merged into the
development branch of the official repository.

It will be officially available on the master branch in the next
release of tinyDTLS.

Other minor updates:
- Support for the RIOT's memarray
- tinydtls/sha2 is removed from the compilation for giving priority
to RIOT's sha2 functions.

boards/stm32l476g-disco: initial basic support

Docs: add "allow time to ACK before dismissing review" to maintainer guidelines

Makefile.include: fix board/cpu inconsistent include order

stm32f103c8: fix Makefile.include INCLUDES definition

As should have been done in the initial commit. Stack space set to the
amount described in the doc

Include order for board and cpu was

1. cpu include
2. board include
3. board common includes
4. cpu common includes

Its now changed to:

1. board include
2. board common includes
3. cpu include
4. cpu common includes

Verifications:

There are no common headers names between boards and cpus.
Except native that has a 'periph_conf.h' in cpu instead of being in board.

tests/driver_pir: remove redundant/double configuration from Makefile

boards/stm32f429i-disc1: add initial support

gnrc_sixlowpan_frag: add asynchronous rbuf GC

While the current approach for garbage collection in the 6Lo reassembly
buffer is good for best-effort handling of
*fragmented* packets and nicely RAM saving, it has the problem that
incomplete, huge datagrams can basically DoS a node, if no further
fragmented datagram is received for a while (since the packet buffer is
full and GC is not triggered).

This change adds a asynchronous GC (utilizing the existing
functionality) to the reassembly buffer, so that even if there is no new
fragmented packet received, fragments older than `RBUF_TIMEOUT` will be
removed from the reassembly buffer, freeing up the otherwise wasted
packet buffer space.

drivers/isrpipe: changed isrpipe_t content order

gnrc_pktbuf_static: fix alignment issue / leaks

pkg/lua: Better Lua-RIOT integration

This example add a module thats starts an interactive READ-EVAL-
PRINT-LOOP written in Lua.

- Remove file related functions from loader.
 * All packages must be builtin.
- Remove os.tmpname.
- Interface with TLSF.
- Don't abort() when out of memory.

Monocypher: Initial import of package

gnrc_sixlowpan_frag: add current_size to exposed struct

Support for monocypher as crypto library. Blazing fast performance, but
double the flash requirement compared to TweetNaCl. Stack usage is
around 70% of TweetNaCl

boards/iotlab-m3|a8: fix openocd configuration