Output buffering is automatically disabled when reading from stdin.
In this case, supplying the -b flag ought to be redundant. However,
since Bflag was being XORed into the flag set - rather than simply
ORed - supplying -b would actually enable output buffering.
add 0xffff to tab1 as range 0xffff-0x10ffff has 4 byte utf-8 sequence.
use Runemax (0x10ffff) instead of Runemask (0x1fffff) to denote
the last valid rune for inverted [^] match as Runemask is out of the
valid rune space.
