Patch tested by compiling with `__attribute__ ((format (printf, 2, 3)))`
applied to `cmd_results_new`.
String usage constants have been converted from pointers to arrays when
encountered. General handler format strings were sometimes modified to
include the old input string, especially for unknown command errors.
Some users may want to switch buttons on their input devices, turns out
libinput already supports it. Let's add a support for it in our config.
Signed-off-by: Michał Winiarski <knr@hardline.pl>
