rump: Port of the rump kernels to Genode

For further information see: http://wiki.netbsd.org/rumpkernel/. In this version
I ported the central rump components to Genode in order to take advantage of
NetBSD file system implementation. The new 'dde_rump' repository contains the
Genode version of the rump libraries and a 'rump_fs' server that implements
Genode file-system-session interface. Currently ext2, iso9660, and fat
file-systems are supported.

Issue #1048