Fix potential memory leak.

If the second memory allocation fails, then we need to free the first.
While we're at it, the zeroing of allocated memory can be replaced by
a call to calloc().

cjellyfish/damerau_levenshtein.c

@@ -14,16 +14,14 @@ int damerau_levenshtein_distance(const char *s1, const char *s2)
     size_t d1, d2, d3, d4, result;
     unsigned short cost;
 
-    size_t *da = malloc(256 * sizeof(size_t));
+    size_t *da = calloc(256, sizeof(size_t));
     if (!da) {
         return -1;
     }
-    for(i = 0; i < 256; i++) {
-        da[i] = 0;
-    }
 
     size_t *dist = malloc((len1 + 2) * cols * sizeof(size_t));
     if (!dist) {
+        free(da);
         return -1;
     }