Always include mythchrono.h videovisualmonoscope.cpp.

This will typically be redundant as it is already included somewhere
in the opengl chain, but it is necessary when compiling with vulkan
but without opengl.

mythtv/libs/libmythtv/visualisations/videovisualmonoscope.cpp

@@ -1,6 +1,7 @@
 #include <algorithm>
 
 // MythTV
+#include "libmythbase/mythchrono.h"
 #include "videovisualmonoscope.h"
 
 #ifdef USING_OPENGL