Fix compilation problem with LaunchServices on OSX

You cannot include the LSOpen.h directly on OSX - it is too far down in
the System hierarchy to locate. Instead we include the umbrella header
CoreServices.h which finds it for us.

Signed off by Amit Chaudhuri <amit.k.chaudhuri@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>