ScriptInterpreterPython needs to save and restore sys.stdout and
friends when LLDB runs a python script.
It currently does this using FILE*, which is not optimal. If
whatever was in sys.stdout can not be represented as a FILE*, then
it will not be restored correctly when the script is finished.
It also means that if the debugger's own output stream is not
representable as a file, ScriptInterpreterPython will not be able
to redirect python's output correctly.
This patch updates ScriptInterpreterPython to represent files with
lldb_private::File, and to represent whatever the user had in
sys.stdout as simply a PythonObject.
This will make lldb interoperate better with other scripts or programs
that need to manipulate sys.stdout.