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.
This modifies `input_cmd_scroll_button` to utilize the mouse button
helper `get_mouse_button` when parsing the button. x11 axis buttons are
not supported with this command and `CMD_INVALID` will be returned, but
all other x11 buttons, button event names, and button event codes should
be working
Now the scroll_button will not accept:
- letters on string beginning;
- negative numbers.
What is tolerated:
- letters after number;
- rational numbers: the fraction after dot will be omitted.
This commit introduces a scroll_button option, which is intended to be
used with scroll_method. Now user can edit his sway config and add an
scroll_button option to device section.
