Add script to detect and remove unCish malloc-then-cast pattern

Also, apply it.

scripts/coccinelle/malloc_cast.cocci

+@cast_malloc@
+expression e;
+type T;
+@@
+- (T *)tor_malloc(e)
++ tor_malloc(e)
+
+@cast_malloc_zero@
+expression e;
+type T;
+identifier func;
+@@
+- (T *)tor_malloc_zero(e)
++ tor_malloc_zero(e)
+
+@cast_calloc@
+expression a, b;
+type T;
+identifier func;
+@@
+- (T *)tor_calloc(a, b)
++ tor_calloc(a, b)
+
+@cast_realloc@
+expression e;
+expression p;
+type T;
+@@
+- (T *)tor_realloc(p, e)
++ tor_realloc(p, e)
+
+@cast_reallocarray@
+expression a,b;
+expression p;
+type T;
+@@
+- (T *)tor_reallocarray(p, a, b)
++ tor_reallocarray(p, a, b)

src/or/circuitstats.c

@@ -691,7 +691,7 @@ circuit_build_times_get_xm(circuit_build_times_t *cbt)
   if (cbt->total_build_times < CBT_NCIRCUITS_TO_OBSERVE)
     num_modes = 1;
 
-  nth_max_bin = (build_time_t*)tor_calloc(num_modes, sizeof(build_time_t));
+  nth_max_bin = tor_calloc(num_modes, sizeof(build_time_t));
 
   /* Determine the N most common build times */
   for (i = 0; i < nbins; i++) {