[mono.data.sqlite] Using sqlite_close_v2 when available

From Matthew Leibowitz (mattleibo)

This is the recommended function for garbage collected languages.
http://sqlite.org/c3ref/close.html

The sqlite3_close_v2() interface is intended for use with host
languages that are garbage collected, and where the order in which
destructors are called is arbitrary.

Falls back to old sqlite3_close if we are on an old system

Useful for ADO.NET where the connection os often closed, but the
commands are re-usable

Mostly visible on Windows operating systems

This snippet should fail with a System.IO.IOException using the
current build of Mono on Windows:

    string filename = "test_" + Guid.NewGuid ().ToString ("N") + ".db";
    SqliteConnection conn = new SqliteConnection ("Data Source=" + filename);
    conn.Open ();
    SqliteCommand cmd = conn.CreateCommand ();
    cmd.CommandText = "PRAGMA legacy_file_format;";
    cmd.ExecuteScalar ();
    // close connection before the command
    conn.Dispose ();
    // then close the command
    cmd.Dispose ();
    // the locks should be released, and we should be able to delete the database
    File.Delete (filename);