Add a utility function smart_iter() which has knowledge of the getsize and the getelem

method names of all the lldb container objects and returns an iterator object when
passed an eligible lldb container object.

Example:

    from lldb_util import smart_iter
    for thread in smart_iter(process):
        ID = thread.GetThreadID()
        if thread.GetStopReason() == lldb.eStopReasonBreakpoint:
            stopped_due_to_breakpoint = True
        for frame in smart_iter(thread):
            self.assertTrue(frame.GetThread().GetThreadID() == ID)
        ...

Add a test case for lldb.smart_iter().

llvm-svn: 130332