Add include guard to constants.h.

ezod · ezod · commit 5c70f6ecccd0 · 2023-10-07T17:17:13.000-04:00
diff --git a/constants.h b/constants.h
@@ -1,2 +1,4 @@
+#pragma once
+
 #define KNOTS_TO_KPH 1.852
 #define KNOTS_TO_MPH 1.15078
