run astyle on all C files in the repository

Leaves parse tests and generated files unchanged, and provides a style
filter for these.

Signed-off-by: Gerwin Klein <gerwin.klein@data61.csiro.au>

licenses: convert license tags to SPDX

misc/autostop: Teach stop how to send SIGABRT and SIGTERM.

misc: Add options to constrain autostop's bloodthirsty rampage.

Autostop is quite handy for keeping your system under control, but when things
go pear shaped the guidance provided by Linux's OOM score doesn't necessarily
align with what the user cares about. In particular, it can take down parts of
your windowing subsystem or a harmless browser tab going about its business.
This commit adds command line options to give autostop a list of processes
which are the only ones you would like stopped. Existing behaviour remains
unchanged.

Import release snapshot.