Reorder the Platform plugin settings so that they're now

platform.plugin.darwin-kernel.kext-directories
platform.plugin.darwin-kernel.search-locally-for-kexts

and fix a few FileSpec handling issues for the kext-directories setting.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@178920 91177308-0d34-0410-b5e6-96231b3b80d8