Operations with Dynamic Lists are not thread-safe, and need to be guarded with mutexes

To implement functionality required by ODBC specs, handles have lists of other handles. For example, (explicit) descriptors have list of statement handles they are used in. That is needed to reset appropriate descriptors in those statements to use default implicit descriptors. And also to remove references to statements when statement handles is free-ed. Also db handle has lists of allocated statements and descriptors. Operations with those lists may cause threaded applications to crash, if not guarded