add placeholders to include files for error messges

src/finish.h

@@ -30,6 +30,11 @@ class Finish : protected Pointers {
 }
 
 #endif
+
 /* ERROR/WARNING messages:
 
+W: Timing breakdown may not be accurate since GPU/CPU overlap is enabled\nUsing 'export CUDA_LAUNCH_BLOCKING=1' will give an accurate timing breakdown but will reduce performance
+
+UNDOCUMENTED
+
 */