WL#5716: NDB Docs: Add auto-linking for kernel blocks

Modify auto-link.xsl and add appropriate  role attribute(s) (something
like "ndbkernel" ought to do the job) so that names of NDB kernel blocks are
linked to the sections describing them in the Cluster Internals section of the
Cluster API Guide.

NOTE: Sometimes these block names are prefixed with "DB", other times not; be
sure to accomodate both styles of usage.

Should otherwise be fairly straightforward.

Should probably be able to fit this in during Dec '10-Jan '11 timeframe.