Added drop for Connection to prevent fd leak
Added drop for Connection to prevent fd leak

Added call to flush_prepared_statement_cache
otherwise InnerConnection receives DatabaseBusy on sqlite3_close

jgallagher/rusqlite,gwenn/rusqlite,mikelodder7/rusqlcipher,xinghun92/rusqlite,xinghun92/rusqlite,gwenn/rusqlite,mikelodder7/rusqlcipher,jgallagher/rusqlite,xinghun92/rusqlite,gwenn/rusqlite,mikelodder7/rusqlcipher,jgallagher/rusqlite