In order to:
- unify sql_yacc.yy and sql_yacc_ora.yy easier
- move more functionality from the parser to Type_handler
  (so plugins can override the behavior)

this patch:
- removes rules sp_param_field_type_string and sp_param_field_type
  from sql_yacc_ora.yy
- adds a new virtial method Type_handler::Column_definition_set_attributes()