The problem was that any VIEW columns had always implicit derivation.
  Fix: derivation is now copied from the original expression
  given in VIEW definition.
  For example:
  - a VIEW column which comes from a string constant
    in CREATE VIEW definition have now coercible derivation.
  - a VIEW column having COLLATE clause
    in CREATE VIEW definition have now explicit derivation.


mysql-test/r/ctype_utf8.result:
  Adding test case
mysql-test/t/ctype_utf8.test:
  Adding test case
sql/field.cc:
  Copying derivation from item to field.
sql/field.h:
  Adding derivation and methods to get/set it into Field.
sql/item.cc:
  Copying derivation from field to item.
sql/item.h:
  Moving "enum Derivation" declaration from item.h to mysql_priv.h
sql/mysql_priv.h:
  Moving "enum Derivation" declaration from item.h to mysql_priv.h
sql/sql_select.cc:
  Copying derivation from item to field in
  create_tmp_field_from_item() and create_tmp_field().