[client] all: properly support guest rotation

If the guest has it's output rotated (ie, landscape) we must rotate and
translate the pointer draw location, as well as all the translations of
cursor coordinate spaces based on the rotation, along with any local
rotations that may also be applied.

client/src/main.h

@@ -54,6 +54,7 @@ struct AppState
   SDL_Point            windowPos;
   int                  windowW, windowH;
   int                  windowCX, windowCY;
+  LG_RendererRotate    rotate;
   bool                 focused;
   SDL_Rect             border;
   SDL_Point            srcSize;