small comment update

src/constants.h

@@ -53,6 +53,8 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #define FOV_ANGLE (PI/2.5)
 
 // The absolute working limit is (2^15 - viewing_range).
+// I really don't want to make every algorithm to check if it's 
+// going near the limit or not, so this is lower.
 #define MAP_GENERATION_LIMIT (31000)
 
 // Size of node in rendering units