Modify pernet_operations check

Modify pernet_operations check

Check for 'int \*id' in the pernet_operations struct
fails for some later versions of kernels as the declaration
is now 'int * const id'.

Kernel Commit 768e4bb6a75e3c6a034df7c67edac20bd222857e changed
the variable declaration that ipset uses to ensure presence
of the pernet ops id.

Modify the pattern match to include both the newer change while
still supporting the original declaration.

Reported and original patch submitted by Mike Pagano <mpagano@gentoo.org>,
single pattern suggested by Jeremy Sowden <jeremy@azazel.net>

Signed-off-by: Jozsef Kadlecsik <kadlec@netfilter.org>