5 b->c mapping codepoints were missed from the new Big5.map file in hkscs2008 putback.

0xA1C4 0xFF3F
0xA2AC 0x2571
0xA2AD 0x2572
0xA451 0x5341
0xA4CA 0x5345

These 5 entries are in Big5.c2b-irreversible. I was misled by the name. It appears that these 5 entries are actually round-trip mappings and should be in the .map/b2c table, I don't know why we put them into the c2b-irreversible at the first place.

The change is relatively easy and straightforward. Move these 5 entries into
Big5.map and remove the Big5.c2b.