Support statements longer than 64KB with native/embedded connections

[mrotteveel]

Since Firebird 3.0, Firebird supports statement texts longer than 64KB (with a server imposed internal limit of 10MB). This is already supported in the pure-java implementation, but not in the native/embedded implementations.

To pass statements longer than 64KB in native/embedded, a Firebird 3.0 or higher client library is required, and a null-terminated string should be offered to isc_dsql_prepare (pass length 0 and a null-terminated string, instead of actual length and normal string).