nrfmin: remove long address support

pkg/nordic_softdevice_ble: Use MAC48 as hardware address

This is just a compatibility issue waiting to happen as soon as there
is support for a more standard-compliant implementation of BLE (like
e.g. NimBLE ;-)).

boards/hifive1: fix file permissions of flasher.sh

cpu/esp32: esp_wifi netdev driver

ESP-IDF heap handling has to be used for esp_wifi for stability reasons. Otherwise, heap is corrupted sporadically

Fixes sporadic blocking of the wifi thread in esp_wifi_recv_cb function under heavy network load conditions when frames are coming in faster than they can be processed. Since esp_wifi_recv_cb function is not executed in interrupt context, the msg_send function used for ISR event can block when the message queue is full. With this change esp_wifi can be flooded with icmpv6 packets of maximum size without any problems over hours.

To avoid further inconsistencies in documentation, README.md is not provided any longer

If WiFi is disconnected, e.g., because of timeout for beacon frame, it is tried to reconnect automatically.

RX callback function should be register when WiFi has been connected to AP successfully and should be unregistered when WiFi disconnects from AP. Therefore, esp_wifi_internal_reg_rxcb is called now in event handler on event SYSTEM_EVENT_STA_CONNECTED. It is reset now on event SYSTEM_EVENT_STA_DISCONNECTED.

Before function wifi_connect is executed, starting the WiFi driver should have been finished. This is indicated by the WiFi driver by sending event SYSTEM_EVENT_STA_START. Function wifi_connect is moved therefore to the event handler for SYSTEM_EVENT_STA_START.

The buffer given by the WiFi driver as parameter eb has to be freed explicitly. Otherwise the esp_wifi_netdev stops working after some seconds.

The WiFi configuration has to be static to avoid memory access problems when WiFi AP is reconnected.

esp_wifi was simply returning the connection state instead of filling the referenced value.

esp_wifi returns false now.

The size of received and transmitted frames was stored in an uint8_t, which did not allow to process frames larger than 255 octets. However, WiFi has an MTU of 1500 octets.

cpu/esp*: compile time configurations for ESP MCUs

Makefile.include: remove functionality to build with another version.

doc/rdm: clarification to revision process

hashes/sha256: don't call memcpy if len==0

fmt: fix fmt_s32_dec() and fmt_s64_dec() sign bit handling

cpu/native/periph/timer: fix type conversion

tests/build_system_utils: fix TESTS name collision

pkg/jerryscript: namespace BUILD_DIR variable

gnrc/pktbuf: avoid memcpy if size <= 0

TESTS is used to find the tests files for the application but was used
to list test targets. Rename to COMPILE_TESTS as already done in some of
my other applications.

BUILD_DIR was introduced but the variable was already used by
`pkg/jerryscript` so there is a name collision.
Namespace it to prevent issues.

cpu/cortexm_common: Update ARM CMSIS to V5.4.0

 gnrc_netif: centralize device-type-specific functions