Allow larger column sizes than 8001 in case DB supports it

In PostgreSQL, the TEXT field can easily have more than 8001 characters
and it does return the actual number. The size == 0 would happen in case
of some DBs won't return valid value where we would keep the same
behavior as of now.

lib/odbc/c_src/odbcserver.c

@@ -1328,7 +1328,7 @@ static db_result_msg encode_column_name_list(SQLSMALLINT num_of_columns,
 				       &nullable)))
 	    DO_EXIT(EXIT_DESC);
 
-	if(sql_type == SQL_LONGVARCHAR || sql_type == SQL_LONGVARBINARY || sql_type == SQL_WLONGVARCHAR)
+	if(size == 0 && (sql_type == SQL_LONGVARCHAR || sql_type == SQL_LONGVARBINARY || sql_type == SQL_WLONGVARCHAR))
 	    size = MAXCOLSIZE;
 
 	(columns(state)[i]).type.decimal_digits = dec_digits;