switch to using calloc (initializes memory to zero)

squiggle_more.c

@@ -225,7 +225,7 @@ void array_print_histogram(double* xs, int n_samples, int n_bins) {
         return;
     }
 
-    int *bins = (int*) malloc((size_t)n_bins * sizeof(int));
+    int *bins = (int*) calloc((size_t)n_bins, sizeof(int));
     if (bins == NULL) {
         fprintf(stderr, "Memory allocation for bins failed.\n");
         return;