Unify grammar rules: field_type_string and sp_param_field_type_string

sql_yacc_ora.yy has two separate set of rules to parse data types:

• field_type, field_type_string - for table fields and SP local variables
• sp_param_field_type, sp_param_field_type_string - SP parameters and SF return values

Let's remove the second set of rules and use field_type/field_type_string for in all cases.
Advantages:

• Unification of sql_yacc.yy and sql_yacc_ora.yy
• Move more code from the *.yy files to Type_handler, so data type plugins have more flexibility.

In order to move the code from *.yy to Type_handler, let's introduce this enum:

enum column_definition_type_t

{

  COLUMN_DEFINITION_TABLE_FIELD,

  COLUMN_DEFINITION_ROUTINE_PARAM,

  COLUMN_DEFINITION_ROUTINE_LOCAL,

  COLUMN_DEFINITION_FUNCTION_RETURN

};

and this virtual method:

virtual bool Column_definition_set_attributes(THD *thd,

                                              Column_definition *def,

                                              const Lex_field_type_st &attr,

                                              CHARSET_INFO *cs,

                                              column_definition_type_t type)

                                              const;

So, for example, Type_handler_varchar::Column_definition_set_attributes() will do the following:

• If the length is specified explictly, set def->length accordingly.
• If the length is not specified explicitly, then
  • In case of a table field type and a local variable type it will return a syntax error
  • In case of an SP parameter type and an SF return type and sql_mode=DEFAULT, it will return a syntax error.
  • In case of an SP parameter type and sql_mode=ORACLE, it will set def in the way that later the formal parameter length is adjusted to the actual parameter length.
  • In case of an SF return type and sql_mode=ORACLE, it will set def->length to the default value (4000).