Follow up on ivykis changes

Between ivykis 0.30 and 0.36 a couple of reorganisations were made,
which needed followups on the syslog-ng side. These are those
folloups:

 * ivykis/lib and ivykis/modules were merged into ivykis/src
 * there is no top-level libivykis.la, it is under src now
 * ivykis/lib/iv_main.c was split, we'll check for
   ivykis/src/iv_main_posix.c now, as that is 0.36 specific, thus
   enforcing that the bundled ivykis is of appropriate version too.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>