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

Also, apply it.

scripts/coccinelle/malloc_cast.cocci

@@ -0,0 +1,38 @@
+@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)