Added an Python operating system plug-in test to verify that python can be...

Added an Python operating system plug-in test to verify that python can be used to add threads to an existing process.

The test does the following:
1 - runs a program to main without the OS plug-in and verifies no OS threads are in the process
2 - loads the OS plug-in and verifies the 3 OS plug-in threads are now in the current process
3 - verify the register contents of each thread that shows up
4 - unload the python OS plug-in and verify that the OS threads are gone.

llvm-svn: 232401