Fix what appears to be an inverted condition in the old regex engine's charlist prefix computation.
Fix what appears to be an inverted condition in the old regex engine's charlist prefix computation.

cygx/nqp,cygx/nqp,cygx/nqp,cygx/nqp,cygx/nqp,cygx/nqp,cygx/nqp,cygx/nqp