<rdar://problem/15936507>

PyTuple_SetItem steals a reference to the item it inserts in the tuple
This, plus the Py_XDECREF of the tuple a few lines below, causes our session dictionary to go away after the first time a SWIG layer function is called - with disastrous effects for the first subsequent attempt to use any functionality in ScriptInterpreterPython
This fixes it



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@200429 91177308-0d34-0410-b5e6-96231b3b80d8