Backslash is non-typeable on some European keyboards(for example Logitech K400+)

[nihirash]

Some keyboards have no backslash near left shift but they have it near enter(above right shift).

Keycode in core_atarist.c that works for this key is under position 32(and marked as EUR-1).

If I replace it with MATRIX(11,4) macros - I have possibility to type backslashes.

I'm using only Atari ST core so I can confirm that this approach will work fine on another cores.

Quick check with all my home keyboards shows that this fix broke nothing but fixes my combo device that I'm using with my tiny Atari build.

[nihirash]

If my changes don't broke anything for rest people and you - one line PR is here: #18