strcat.3: Fix off-by-one error in example code

Reported-by: Eric Sanchis <eric.sanchis@iut-rodez.fr>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man3/strcat.3

@@ -209,7 +209,7 @@ main(int argc, char *argv[])
 {
 #define LIM 4000000
     int j;
-    char p[LIM];
+    char p[LIM + 1];    /* +1 for terminating null byte */
     time_t base;
 
     base = time(NULL);