On MacOSX, the threads can appear out of order at times depending on the order...

On MacOSX, the threads can appear out of order at times depending on the order in which the kernel returns thread IDs to debugserver. To avoid thread lists changing order between stops, ProcessGDBRemote now makes sure the thread list stays sorted by thread index ID.

<rdar://problem/25501013> 

llvm-svn: 272444