[AppKit] Fix prototype to use an IntPtr.
[AppKit] Fix prototype to use an IntPtr.

As per http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/ApplicationKit/Classes/NSWorkspace_Class/Reference/Reference.html#//apple_ref/occ/instm/NSWorkspace/launchAppWithBundleIdentifier:options:additionalEventParamDescriptor:launchIdentifier: the final NSNumber argument is a double pointer and should be set to NULL hence the type change to IntPtr.

The previous definition was causing a SIGSEGV.

dlech/monomac,PlayScriptRedux/monomac