Rules.c: Do not convert from internal to target encoding in case we are
running hybrid mask. It will happen in mask.c after applying the mask.
Mask mode: Reject 8-bit "codepage" placeholders with UTF-8 encoding.
Mask mode: Cosmetic/whitespace.
For pure mask mode using internal encoding, skip conversion if our mask
(after current truncation) can't actually produce any 8-bit characters.
This can make for up to a 2x performance boost.