Bug#30081: "ON UPDATE CURRENT_TIMESTAMP" wasn't shown by the SHOW FIELDS

command and reported to a client.

The fact that a timestamp field will be set to NO on UPDATE wasn't shown 
by the SHOW COMMAND and reported to a client through connectors. This led to
problems in the ODBC connector and might lead to a user confusion.

A new filed flag called ON_UPDATE_NOW_FLAG is added. 
Constructors of the Field_timestamp set it when a field should be set to NOW
on UPDATE.

The get_schema_column_record function now reports whether a timestamp field
will be set to NOW on UPDATE.


mysql-test/t/information_schema.test:
  A test case adjusted after fixing the bug#30081.
mysql-test/r/type_timestamp.result:
  Adjusted a test case after fixing bug#30081.
mysql-test/r/type_ranges.result:
  Adjusted a test case after fixing bug#30081.
mysql-test/r/show_check.result:
  Adjusted a test case after fixing bug#30081.
mysql-test/r/ps_5merge.result:
  Adjusted a test case after fixing bug#30081.
mysql-test/r/ps_4heap.result:
  Adjusted a test case after fixing bug#30081.
mysql-test/r/ps_3innodb.result:
  Adjusted a test case after fixing bug#30081.
mysql-test/r/ps_2myisam.result:
  Adjusted a test case after fixing bug#30081.
mysql-test/r/metadata.result:
  Adjusted a test case after fixing bug#30081.
mysql-test/r/log_tables.result:
  Adjusted a test case after fixing bug#30081.
mysql-test/r/information_schema.result:
  A test case adjusted after fixing the bug#30081.
mysql-test/r/grant.result:
  Adjusted a test case after fixing bug#30081.
tests/mysql_client_test.c:
  A test case adjusted after fixing the bug#30081.
sql/sql_show.cc:
  Bug#30081: "ON UPDATE CURRENT_TIMESTAMP" wasn't shown by the SHOW FIELDS
  command and reported to a client.
  The get_schema_column_record function now reports whether a timestamp field
  will be set to NOW on UPDATE.
sql/field.cc:
  Bug#30081: "ON UPDATE CURRENT_TIMESTAMP" wasn't shown by the SHOW FIELDS
  command and reported to a client.
  Constructors of the Field_timestamp set the ON_UPDATE_NOW_FLAG on a field when
  it should be set to NOW on UPDATE.
include/mysql_com.h:
  Bug#30081: "ON UPDATE CURRENT_TIMESTAMP" wasn't shown by the SHOW FIELDS
  command and reported to a client.
  A new filed flag called ON_UPDATE_NOW_FLAG  is added.
client/mysql.cc:
  Bug#30081: "ON UPDATE CURRENT_TIMESTAMP" wasn't shown by the SHOW FIELDS
  command and reported to a client.
  The fieldflag2str function is adjusted to print the ON_UPDATE_NOW_FLAG.

tests/mysql_client_test.c

@@ -7787,7 +7787,7 @@ static void test_explain_bug()
   verify_prepare_field(result, 5, "Extra", "EXTRA",
                        mysql_get_server_version(mysql) <= 50000 ?
                        MYSQL_TYPE_STRING : MYSQL_TYPE_VAR_STRING,
-                       0, 0, "", 20, 0);
+                       0, 0, "", 27, 0);
 
   mysql_free_result(result);
   mysql_stmt_close(stmt);