Functions, Structs and Parameters definitions on kernel documentation
are pure cosmetic, it only highlights the element.

To ease the navigation in the documentation we should use <links> inside
those tags so readers can easily jump between methods directly.

This was discussed in 2014[1] and is implemented by getting a list
of <refentries> from the DocBook XML to generate a database. Then it looks
for <function>,<structnames> and <paramdef> tags that matches the ones in
the database. As it only links existent references, no broken links are
added.

[1] - lists.freedesktop.org/archives/dri-devel/2014-August/065404.html
Signed-off-by: Danilo Cesar Lemes de Paula <danilo.cesar@collabora.co.uk>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Stephan Mueller <smueller@chronox.de>
Cc: Michal Marek <mmarek@suse.cz>
Cc: intel-gfx <intel-gfx@lists.freedesktop.org>
Cc: dri-devel <dri-devel@lists.freedesktop.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>