Currently Trace-log file was writed by using codepage of user connection.
This is potential trouble with using several codepage at a one time.
In the end-user implementation traceplugin we may be use TraceSQLStatement::getTextUTF8(), but has no analog for the statement paramenters.
Improvement request: new method of interface trace-plugin
size_t TraceConnection::convertToUTF8(const char *src, size_t src_size, char *dst, size_t dst_size);
returns the number of char actually converted