Ruby

encoding.c: encoding check

• encoding.c (enc_check_encoding): use is_data_encoding() to check
  type consistently.
• encoding.c (must_encoding): return rb_encoding* instead of encoding
  index.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41968 b2dd03c8-39d4-4d8f-98ff-823fe69b080e