Disallow also Unicode ranges 0xFDD0..0xFDEF and

Disallow also Unicode ranges 0xFDD0..0xFDEF and
0xFFFE..0xFFFF.  Ranges 0x...FFFE..0x...FFFF in general,
and characters beyond 0x10FFF should be disallowed, too,
but some tests would need changing, but more importantly some
APIs would need remodeling since one can easily generate such
characters either by bitwise complements, tr complements, or
v-strings.

p4raw-id: //depot/perl@13722