Codechange: using "until" in function names can be confusing

IsSavegameVersionUntil() did a [0, N] check, not [0, N) as the
name suggests.

Until can be a confusing word, where people consider it to be
including the upperbound. Dictionary states it means "before",
excluding the upperbound. There are long debates about who is right.

So, simply remove away from this ambiguity, and call it "before"
and "before or at". This makes the world easier for everyone.