Iniitialize and Setup the StreamContext associated with a File

This fixes

   get_stream_context(CVarRef stream_or_context)

so that it works for streams as well as contexts which in turn means that

   stream_context_get_params($stream_or_context)

 and

   stream_context_get_options($stream_or_context)

will now also work for streams.
TempFile::sweep shouldn't free smart allocated objects