Make sure that the CommandInterpreter::m_command_io_handler_sp gets reset when we quit.

Currently if you run _any_ python, python has the "lldb.debugger" global variable and it has a strong reference to a lldb_private::Debugger since it is a lldb::SBDebugger object with a shared pointer.

This makes sure that your LLDB command interpreter history is saved each time you quit command line LLDB.

llvm-svn: 207164
diff --git a/lldb/source/Interpreter/CommandInterpreter.cpp b/lldb/source/Interpreter/CommandInterpreter.cpp
index 1ee5736..980a45a 100644
--- a/lldb/source/Interpreter/CommandInterpreter.cpp
+++ b/lldb/source/Interpreter/CommandInterpreter.cpp
@@ -351,6 +351,12 @@
     }
 }
 
+void
+CommandInterpreter::Clear()
+{
+    m_command_io_handler_sp.reset();
+}
+
 const char *
 CommandInterpreter::ProcessEmbeddedScriptCommands (const char *arg)
 {