Remove eval-when-compile.

Remove eval-when-compile.
(viet-viscii-nonascii-translation-table): Define it as a
translation table made from viet-viscii-decode-table.
(viet-viscii-encode-table): Define it as a translation table made
from the reverse map of above.
(viet-vscii-nonascii-translation-table): Define it as a
translation table made from viet-vscii-decode-table.
(viet-vscii-encode-table): Define it as a translation table made
from the reverse map of above.
(ccl-decode-viscii): Use translate-character.
(ccl-encode-viscii, ccl-encode-viscii-font)
(ccl-decode-vscii, ccl-encode-vscii, ccl-encode-vscii-font):
Likewize.