Add functionality for overlay tweaking & manual capturing by apps

* The functionality is exposed via dllexported functions so that apps can
  call it to tweak renderdoc's behaviour when injects.
  1) Can now turn bits of the overlay off, or hide it entirely.
  2) Can also manually start and stop a capture on a given window. This
     skips the need for swapping between active swapchains, and allows the
     app to define the exact region of D3D11 calls to be captured (could in
     fact be many frames).
     The window provided determines the swapchain used for thumbnail, and
     also implicitly specifies the device to be used for capture.

renderdoc/replay/entry_points.cpp

@@ -194,12 +194,42 @@ uint32_t RENDERDOC_CC RENDERDOC_InjectIntoProcess(uint32_t pid, const wchar_t *l
 	return Process::InjectIntoProcess(pid, logfile, opts, waitForExit);
 }
 
+extern "C" RENDERDOC_API
+void RENDERDOC_CC RENDERDOC_SetActiveWindow(void *wndHandle)
+{
+	RenderDoc::Inst().SetActiveWindow(wndHandle);
+}
+
 extern "C" RENDERDOC_API
 void RENDERDOC_CC RENDERDOC_TriggerCapture()
 {
 	RenderDoc::Inst().TriggerCapture();
 }
 
+extern "C" RENDERDOC_API
+void RENDERDOC_CC RENDERDOC_StartFrameCapture(void *wndHandle)
+{
+	RenderDoc::Inst().StartFrameCapture(wndHandle);
+}
+
+extern "C" RENDERDOC_API
+bool RENDERDOC_CC RENDERDOC_EndFrameCapture(void *wndHandle)
+{
+	return RenderDoc::Inst().EndFrameCapture(wndHandle);
+}
+
+extern "C" RENDERDOC_API
+uint32_t RENDERDOC_CC RENDERDOC_GetOverlayBits()
+{
+	return RenderDoc::Inst().GetOverlayBits();
+}
+
+extern "C" RENDERDOC_API
+void RENDERDOC_CC RENDERDOC_MaskOverlayBits(uint32_t and, uint32_t or)
+{
+	RenderDoc::Inst().MaskOverlayBits(and, or);
+}
+
 extern "C" RENDERDOC_API
 void RENDERDOC_CC RENDERDOC_QueueCapture(uint32_t frameNumber)
 {