FreeBSD: fix sys/sysctl.h #ifdef
FreeBSD: fix sys/sysctl.h #ifdef

Thanks to Pavan Balaji.

This commit was SVN r5587.

ggouaillardet/hwloc,shekkbuilder/hwloc,shekkbuilder/hwloc,ggouaillardet/hwloc,shekkbuilder/hwloc,ggouaillardet/hwloc,ggouaillardet/hwloc,shekkbuilder/hwloc