Add a small interface into Qt widgets to our own python wrapping

* This by no means replaces PySide2, but it allows python extensions to write
  simple UIs without needing to rely on PySide2, which might not be available
  (generally all windows builds have it as well as recent binary linux builds,
  but local windows builds may not and most linux builds probably won't).

qrenderdoc/Code/pyrenderdoc/PythonContext.h

@@ -52,6 +52,9 @@ public:
   void Finish();
 
   PyThreadState *GetExecutingThreadState() { return m_State; }
+  void PausePythonThreading();
+  void ResumePythonThreading();
+
   static void GlobalInit();
   static void GlobalShutdown();
 
@@ -131,6 +134,9 @@ private:
   // not
   PyThreadState *m_State = NULL;
 
+  // this is stored so we can push/pop the GIL state properly
+  void *m_SavedThread = NULL;
+
   struct
   {
     QString file;