libipvs-2.6: sync with libipvs from ipvsadm 1.27
Reapply: Only define kernel types for ip_vs.h header to avoid problems when loading other headers.
Reapply: Avoid the use of kernel defines in libipvs userland prototypes

* fix libipvs-2.4 ipvs_get_service(...) prototype to use
  ISO types instead of kernel ones...
* fix libipvs-2.6 ipvs_get_service(...) prototype to use
  ISO types instead of kernel ones...

Conflicts:
	keepalived/libipvs-2.6/libipvs.h
libnl >= 3 support
libipvs: add nlerr2syserr function to translate libnl 3 errors to sys errors