Center setup menu title patches

[xemonix0]

The hardcoded positions assume very specific patches, e.g. M_COMPAT is assumed to say "Doom Compatibility" (even though nowadays the alt. text is "Compatibility", and I'd expect a patch saying the exact same in BIGFONT to work perfectly fine) and M_STAT is assumed to say "Status Bar / HUD` (with spaces, unlike the modern alt. text).

What I did (with x == -1 meaning centered) may not be the best way to do it so I expect a change request. Also, I did not center the patches that I think are supposed to be off-center (M_EPISOD, M_NEWG, M_SKILL, M_LOADG, M_SAVEG; looks like they are supposed to be positioned relatively to the items and not the screen, and I feel like they should be kept at their vanilla positions anyways).

[fabiangreffrath]

I'd prefer if you could #define M_X_CENTER -1 in some header and use this consistently.

[xemonix0]

I'd prefer if you could #define M_X_CENTER -1 in some header and use this consistently.

Done in 2598e52.

[fabiangreffrath]

LGTM, thank you!

What do the others say?

[ceski-1]

I like it!

[rfomin]

Thank you.