nodeinfo: make freebsdNodeGetCPUCount work on Mac OS X

nodeinfo: make freebsdNodeGetCPUCount work on Mac OS X

This fixes the following error:
  error : nodeGetInfo:933 : this function is not supported
  by the connection driver: node info not implemented on this platform

The freebsdNodeGetCPUCount was renamed to appleFreebsdNodeGetCPUCount
in order to make more visible the fact, that it works on Mac OS X too.

Mac OS X can use sysctlbyname as same as FreeBSD to get the CPU
frequency. However, the MIB style name is different from FreeBSD's.
And the unit of the return frequency is also different.

Signed-off-by: Ryota Ozaki <ozaki.ryota@gmail.com>
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>