doc/doxygen: enable parsing of packages docs

pkg/semtech-loramac: small fixes

boards/nucleo-l152: configure LSI by default

cc2538/include/periph_cpu.h: Changed UART configuration format for cc2538.

gnrc_rpl: allow for non-router operation (as leaf)

- link to loramac-node github repository is broken
- the example code should return after a failed join procedure

driver/adxl345: rename enums to avoid conflicts

Exception are made for emb6, nordic_softdevice_ble, openthread and semtech-loramac because their documentation contains warning/issues

makefiles: Add an APPLICATION_MODULE variable

isrpipe: fix timeout unit in api documentation

netdev: Add Netdev to Doxygen page title

sys/phydat: Introduce PHYDAT_MIN, PHYDAT_MAX

sys/rtt_stdio: reserve file descriptors for stdin, stdout, and stderr

This makes sure that stdio works as expected when sys/rtt_stdio and sys/vfs
are used at the same time.

boards/b-l072z-lrwan1: add I2C configuration

gnrc/netif: fix source address selection for non-matching prefixes

doc: replace conn with sock in GNRC architecture overview

tests/pkg_semtech_loramac: fix get command with EUI values

tests/pkg_semtech-loramac: fix loramac set devaddr

crypto/cbc: add return values to documentation

SAUL/phydat: parts per million support

sys/phydat: rename phydat_scale_to_str -> phydat_prefix_from_scale

drivers/sdcard_spi: use of ucrc16 by default

Useless consts removed.

drivers: Initial import of low-level QDEC driver interface

unittests/tests-core: Fix tests in loop not being executed

Correct some outdated documentation and make the name represent what the
function does today.

mtd_native: fix overlapping pages write check