Added the ability to set the Platform path for a module through the SBModule

interface.

Added a quick way to set the platform though the SBDebugger interface. I will
actually an a SBPlatform support soon, but for now this will do.

ConnectionFileDescriptor can be passed a url formatted as: "fd://<fd>" where
<fd> is a file descriptor in the current process. This is handy if you have
services, deamons, or other tools that can spawn processes and give you a
file handle.

llvm-svn: 130565