Add a simple test for PrintStackTrace crash

I realized that crashes that are happening only when executed with swift, but not swiftc, are probably due a bug in PrintStackTrace itself. This is a simple test case that illustrates the situation. The program should compile and then crash when executed with stack trace printed, but it is actually the PrintStackTrace that is crashing after the program has crashed. 

We need to wait to see how to handle '.script.' crashes, when this bug is fixed.