Add libuutil to LIBADD for libzfs and libzfs_core

Resolve spurious dpkg-shlibdeps warnings like this:

	warning: symbol strlcpy used by libzfs_core.so found in none of the libraries

This happens because dpkg-shlibdeps does not recursively search for symbols.
Resume dh_shlibdeps reporting.

Various upstream, toolchain, and distro improvements have dh_shlibdeps
returning a reasonable number of actionable complaints.
Add patch: Fix zil_commit() NULL dereference

Cherry-pick 908a0c2822f7b00f4339a6c2e8f351451a15a2be into the patch queue. This
is the only update in the zfs-0.6.3-stable branch that is pertinent for Ubuntu
installations as of the META 0.6.3-1.1 release.