Closed Stale PRs for 2020.01

List of PR's that where closed during 2020.01 release cycle. is:pr label:"State: stale" closed:>2019-10-01 is:closed

#11459 [WIP] doc: Sphinx for documentation / second attempt.

#11416 drivers/hx711: driver and SAUL adaption for the HX711 sensor

#11369 WIP: introduce periph_sleepmem

#11203 sys/riotboot: extend Makefile.include include to riotboot feature

#11107 cpu/stm32_common: prevent uart write stuck

#11069 core: Added thread_signal & thread_await_signal

#10976 doxygen/Makefile: summarize warnings, log full output to file.

#10494 mcuboot.mk: refactor into a declarative-style makefile.

#10393 Improve and debug Xtimer

#10355 radios: Remove default radio flags from init

#9818 git-lfs: add support for board documentation files

#9258 sys/newlib: Split stubs and make modules provide non-stubs

#9194 board/cpu init: move cpu_init() from board_init() to startup

#8784 sys/shell: switch stdout to unbuffered mode

#8564 Improve shell_commands

#7315 samd21:setup all clock generators in clock.c

#7086 drivers: add GPS API

#6923 [RFC] make: introduce driver specific Makefiles for .dep and .include