Undo soname bump

The soname was bumped before 3.2.18 was released to reflect
an ABI change in the cache and object API.

This caused a discussion with various distribution maintainers
involved as it prevented them from including the release in
their stable branches. This is especially unfortunate as the
corresponding API is unused outside of libnl as of now.

For this reason, I have decided to undo the soname bump and
instead remove the corresponding header files from the list of
installable headers and thus remove them from the public API.

This is a API break technically but since nobody is using
them it should not matter. If you are in fact using any of the
*-api.h headers please let me know and we are most likely to
start a new development branch.

If your application linked against 3.2.18 or 3.2.19 you will need
to relink if you want it to use >= 3.2.20.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
No longer install module API headers

Various header files providing an API to implement own cache and
object types or implement link types have been available in the
past. Their API is marked unstable in the documentation and nobody
is using them so far.

Technically they have been causing ABI breakages in at least two
3.2.x releases. In order to avoid future accidental breakage, no
longer install these and require module developers to clone the
git tree and build modules off the git tree directly to make sure
that the API is unstable at this point.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Remove obsolete release notes at end of configure

Signed-off-by: Thomas Graf <tgraf@suug.ch>
route cache: This patch adds route priority to route object oo_id_attrs

The kernel allows multiple entries in the main table which differ in the
priority value. In libnl currently, since priority is not part of the base
netlink route message, it is not used as part of the key. This patch
includes priority in the key/oo_id_attrs and defaults the value to zero
for messages where priority is not included.

One point to note is that the actual selection of route from multiple
options is done implicitly in the kernel by storing the routes in sort
priority order, but there is no explicit communication to a client of libnl
of that.

Signed-off-by: Shrijeet Mukherjee <shm@cumulusnetworks.com>
Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: Thomas Graf <tgraf@suug.ch>
3.2.20 release