Move analogue mode filter update logic to fixed-timestep loop

Otherwise if the analogue filter is scrolling, it'll scroll by REALLY
fast.

desktop_version/src/main.cpp

@@ -486,6 +486,11 @@ int main(int argc, char *argv[])
                 graphics.updatescreenshake();
             }
 
+            if (graphics.screenbuffer->badSignalEffect)
+            {
+                UpdateFilter();
+            }
+
             //We did editorinput, now it's safe to turn this off
             key.linealreadyemptykludge = false;