Do not build Db4objects from source, as it does not seem to compile with the latest Mono. Use a precompiled assembly.

Signed-off-by: Xavi Artigas <xartigas@fluendo.com>
Make sure the target directory exists before installing the db4o assembly.

Signed-off-by: Xavi Artigas <xartigas@fluendo.com>
Remove unneeded patches.