Add functionality to return raw thumbnail bytes, not encoded

* This is useful if you want to retrieve the thumbnail for in-memory
  processing instead of writing it to disk immediately.

renderdoccmd/renderdoccmd.cpp

@@ -296,7 +296,7 @@ struct ThumbCommand : public Command
     ReplayStatus st = file->OpenFile(filename.c_str(), "rdc");
     if(st == ReplayStatus::Succeeded)
     {
-      buf = file->GetThumbnail(type, maxsize);
+      buf = file->GetThumbnail(type, maxsize).bytes;
     }
     else
     {