Added a flag (_send_traceback_header) to the SimpleXMLRPCServer class

Added a flag (_send_traceback_header) to the SimpleXMLRPCServer class
that allows sending back exception/stack trace information about
internal server errors (this flag defaults to False to avoid sending
such information unless explicitly enabled).  Added tests to verify
behavior of this new feature (these tests are skipped on win32 because
of problems with WSAEWOULDBLOCK). Renamed HTTPTestCase to
SimpleServerTestCase. [GSoC - Alan McIntyre]