Allows you to change viewing range using numpad +/- again. This fix also works with the current unreleased version of SDL 3.
The keycodes for numpad keys (both SDL keycodes and Irrlicht keycodes) are not the same as the keycodes for the equivalent non-numpad keys and don't correspond to chars, so I mapped them to chars manually.
Since I think the resolution of https://github.com/minetest/minetest/issues/13770 was "just disable numlock", I made sure to only do this for the numpad number keys if numlock is enabled.
It now works even if window creation succeeds and only context creation fails.
Adapted from https://github.com/MoNTE48/Irrlicht . This should be fine
license-wise since that repo still contains the original Irrlicht license
(this is no legal advice).
Original PR: https://github.com/MoNTE48/Irrlicht/pull/9
Co-authored-by: Deve <deveee@gmail.com>
