TPCFmtMsg: Use layout markup for assist messages.
Remove percent sign sanitization altogether.

We *are* going to introduce custom sprintf format strings once we're doing hardcoded strings. Anywhere else, this is a buffer overflow vulnerability that needs to be fixed in the game itself.
Use a separate type variable for the slot and time index.

... really, h1 is the only instance in which we make use out of this feature anyway, it's just an annoyance anywhere else.
Refactor prefix and postfix constants for special types into an array.
Add support for the tabchar type.