[amaralthalesalves]

Closes #752.

Both pad paths cut each stick axis at XInput's 7849 (about 24%): pad_sdl.c's stick_value and nn_hid.c's XInput pads_read. They now go through one function, hos_stick_axis(v, zone) in nn_hid.c, with the threshold chosen by a new Insert menu row on the Controls tab:

• Stick dead zone: Default (24%), 5%, 10%, 15%, 20%, 30%. It's saved as stick_dead_zone in hookshot_options.ini by the same row-name mechanism as the other options, and clamped to 0..5.
• Menu option id 18 (vk_replay.cpp's t.option). Like the other controls rows, it doesn't move the quality preset to Custom.
• At Default the output is the same as before for every input on both paths, so options_version isn't bumped: an ini without the key reads as 0, which is today's behaviour.
• The cut is per axis and only the threshold changes; there's no anti-dead-zone scaling. The game's own dead zone still applies after ours, which the row's help text and the readme say.

Tests: tests/test_stick_dead_zone.py, registered in run_all.py with gcc/g++.

• It compiles the real hos_stick_axis and stick_value with gcc -Wall -Werror and checks them against copies of the old XInput and SDL code for all 65536 inputs at Default, plus each threshold's edges in both directions and out-of-range zones.
• Through g++ it uses the real Row, tx_stick_dead_zone, ini_key and menu_init's parse line: it checks clamping (3, 9, -4, x, a misspelled key) and the labels.
• It also checks in the source that id 18 is wired, that the row doesn't reset the preset, and that the readme row is there.

$ python -I -B tests/test_stick_dead_zone.py          # main
FAIL: nn_hid.c has no hos_stick_axis
$ python -I -B tests/test_stick_dead_zone.py          # this branch
stick: Default is the old cut for all 65536 inputs, both paths; 5 other thresholds exact
menu: stick_dead_zone parses and clamps to 0..5; labels Default (24%) ... 30%
ok

The related input, rumble, text-speed and mouse tests pass. nn_hid.c and pad_sdl.c pass gcc -fsyntax-only -Wall, and vk_menu.cpp and vk_replay.cpp pass g++ -fsyntax-only.

Not verified: I have no game or GPU here, so I haven't seen the row drawn on screen or played with the lower settings.

[amaralthalesalves]

Closing for now: this is a feature request rather than a bug fix, and I'd rather leave feature decisions to the maintainers. The branch stays up if anyone wants to pick it up.