shell/ifconfig: Fixed stringification

cpu/native: fix race in thread_yield_higher()

net stats: move layer 2 netstats from netdev driver to gnrc_netif

Removing usage of netdev->stats in all net drivers, as it is
handled by gnrc_netif.

tests/periph_rtt: add Python script for automatic testing + use 5s delay between Hellos

This removes the netopt to get layer 2 netstats from netdev.

This the first step in moving the collection of layer 2 netstats from
the low level driver to a central location, ie. gnrc_netif, to avoid
code duplication.

RFC: UART enhanced settings

drivers/sds011: Fix error return value on SAUL driver

add driver for SDS011 active laser dust sensor

Add positive and negative tests for data bits, stop bits and parity:

- 7E1, 7O1
- 8E1, 8O1
- 8N2

Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>

Add command mode that will be used like this:

mode <dev> <data bits> <parity> <stop bits>

This command must be called after init otherwise
the UART won't be fully initialized.

Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>

Add support for specifying data bits, stop bits and parity at
runtime.

Introduce feature periph_uart_modecfg for uart_mode() till all
other CPUs implement it.

STM32 L1, F1, F2, F4 supports following modes:

* 7E1, 7E2
* 7O1, 7O2
* 8N1, 8N2
* 8E1, 8E2
* 8O1, 8O2

STM32 L0, L4, F0, F3, F7 supports following modes:

* 6E1, 6E2
* 6O1, 6O2
* 7E1, 7E2
* 7O1, 7O2
* 7N1, 7N2
* 8N1, 8N2
* 8E1, 8E2
* 8O1, 8O2

Use USART_CR1_M1 macro to detect 7-bit support because
even inside one family there could be devices that don't
support 7-bit mode. So just using a family macro is not
enough.

As stated in the datasheets for L0, L4, F0, F3, F7 devices,
data bits can only be changed when UART is disabled (UE=0).
Introduce uart_stop() routine to satisfy this requirement.

STM32 UART adds parity to the MSB of a byte to send. The same
also applies to the received bytes. As a result this bit must
be masked in order to get the pure data.

Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>

As suggested in PR#5899 add a routine uart_mode() that will
setup data bits, stop bits and parity at runtime.

uart.h provides a set of enums defining these settings and each
platform will override them to specify values corresponding to
its configuration registers.

The idea behind the enums is to specify default settings i.e. 8N1
through the 0 value item. Invoking uart_mode(uart, 0, 0, 0) will
setup 8N1 mode.

Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>

pkg/semtech-loramac: improve TX status management after sending a message

github: fix security bug template

cpu/saml21: extend and fix exti configuration for saml21 variants

cpu/esp8266: Fixes and improvements of esp_wifi netdev driver

Added a configuration for saml21g18a and fixes the configuration for samr30g18a

.github: add big warning signs about security bugs

sock_dns: correctly report too short messages