Ruby

• tool/transcode-tblgen.rb (transcode_compile_tree): make
  valid_encoding mandatory unless from_encoding is registered in
  ValidEncoding.
  (transcode_tbl_only): ditto.
  (transcode_tblgen): ditto.
  (ValidEncoding): new function.

• enc/trans/escape.trans: specify valid_encoding.

• enc/trans/emoji_sjis_docomo.trans: ditto.

• enc/trans/emoji.trans: ditto.

• enc/trans/emoji_iso2022_kddi.trans: ditto.

• enc/trans/big5.trans: ditto.

• enc/trans/emoji_sjis_softbank.trans: ditto.

• enc/trans/emoji_sjis_kddi.trans: ditto.

• enc/trans/chinese.trans: use ValidEncoding() instead of
  ValidEncoding[].

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@26995 b2dd03c8-39d4-4d8f-98ff-823fe69b080e