IB: update foreign constraints of timestamp-based versioned tables

[midenok]

Related to #209. See this in row0mysql.cc:

		if (vers_set_fields && !prebuilt->versioned_write)
		{
			// FIXME: timestamp-based update of sys_trx_end in run_again
			err = DB_UNSUPPORTED;
			trx->error_state = err;

			goto handle_error;
		}

[midenok]

Row is converted to innobase by row_mysql_convert_row_to_innobase(). Field is converted to innobase like this:

		row_mysql_store_col_in_innobase_format(
			dfield,
			prebuilt->ins_upd_rec_buff + templ->mysql_col_offset,
			TRUE, /* MySQL row format data */
			mysql_rec + templ->mysql_col_offset,
			templ->mysql_col_len,
			dict_table_is_comp(prebuilt->table));

[midenok]

TODO:

1. get query start time in Field format on SQL side. Impossible to do this on IB side because timestamps are stored in SQL-specific format and presented to IB as DATA_FIXBINARY.
2. get Field buffer from SQL in IB;
3. translate Field buffer into IB format with row_mysql_store_col_in_innobase_format().

[midenok]

It would be good to have TABLE for dict_table_t, but it is unavailable. Currently it can be cached in vc_templ (innobase_find_mysql_table_for_vc(), find_fk_open_table() ). Though vc_templ is for virtual columns and is not built without them.