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Correct RANGECHECK macro in Black Box

Lasers are numbered from 0 to nlasers-1 inclusive, so the upper limit
should be "<", not "<=".

--- a/blackbox.c

+++ b/blackbox.c

@@ -305,7 +305,7 @@

 #define GRID(s,x,y) ((s)->grid[(y)*((s)->w+2) + (x)])

-#define RANGECHECK(s,x) ((x) >= 0 && (x) <= (s)->nlasers)

+#define RANGECHECK(s,x) ((x) >= 0 && (x) < (s)->nlasers)

 /* specify numbers because they must match array indexes. */

 enum { DIR_UP = 0, DIR_RIGHT = 1, DIR_DOWN = 2, DIR_LEFT = 3 };