Loose the check for dead keys

[daxian-dbw]

In #933, I tried to use the win32 API ToUnicode to check for dead keys -- according to the documentation, if the return value is -1 or >=2, the key is most likely a dead key.
However, it turns out ToUnicode is not reliable when the keyboard is not natively supported by Windows. For example, with the Neo keyboard, ToUnicode seems to return 0 for dead keys. So the fix could be to loose the check for dead keys -- treat a key as a dead key as long as ToUnicode failed to translate.

I haven't set up the Neo keyboard yet ... so I haven't tried this fix myself. Will update once I got the Neo keyboard correctly added.

/cc @Snaptags and @MovGP0, can you please try out this fix on your Neo keyboard?

[Snaptags]

That does look better, but only as far as the modifier keys are concerned (Caps-Lock, right Alt), they don't enter the "@" any longer.

But the problem of duplicated "dead keys" remains, i.e.
à` â^ instead of just a` a^

This is where the dead keys are located using the Neo2 layout:

They are used to modify the NEXT character inserted, that is I enter <^> and then <a> to get â. Or <a>, <^> and then <space> to get a^ PSReadline applies the dead key to already entered characters, too.

[daxian-dbw]

Thanks @Snaptags for the feedback. I will close this PR in favor of #945