vsqlite++ 0.4.2

Patch release that fixes a regression introduced while hardening query/result statement lifetimes
in 0.4.1.

Fixes

Fixed sqlite::command statement ownership so prepared statements are no longer finalized by a
temporary statement_handle during preparation.
Deleted statement_handle copy/move operations to prevent future double-finalize or premature
finalize regressions.
Restored backup and execute paths that crashed when sqlite3_step() received the prematurely
finalized statement pointer.