Minor dialog tweaks

Draw 16 characters at a time to reduce confusion about Valkyria Chronicles passwords, and anyway, 16 seems like a likely limit compared to 15, and gives more than enough room still.

Also use the latch to read characters.  Unlike `__CtrlPeekButtons()` which tells you exactly what buttons are pressed now, the latch alternates with rapid fire.  This allows rapid fire to apply to save dialogs as well, which I prefer.

Lastly is the most possibly controversial change (for those who prefer dialogs to be emulated exactly): allow OK/confirm to accept a "Savedata loaded" confirmation screen.  The PSP itself requires you to press back/cancel, but this message is not a message users generally need to confirm in that way.

In contrast, saved, deleted, no data, etc. are messages that it makes more sense for users to read, even if they're mashing x.

This UX choice can be found in most games that use their own custom save UI (rather than the PSP's dialog.)

-[Unknown]