ScriptInterpreterPython: %p should be used with void-pointer

printf's %p format specifier expects an argument of type void-pointer,
not type PyThreadState*.  Fix this with a static_cast.

Differential Revision: http://reviews.llvm.org/D4632

git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@213695 91177308-0d34-0410-b5e6-96231b3b80d8