[cff-subset] Adjust pre-allocation

Reduces memory use significantly.

src/hb-cff-interp-common.hh

@@ -522,7 +522,7 @@ struct parsed_values_t
 
   void alloc (unsigned n)
   {
-    values.alloc (n);
+    values.alloc (n, true);
   }
 
   void add_op (op_code_t op, const byte_str_ref_t& str_ref = byte_str_ref_t ())

src/hb-subset-cff-common.hh

@@ -644,7 +644,7 @@ struct subr_subsetter_t
       ENV env (str, acc, fd);
       cs_interpreter_t<ENV, OPSET, subr_subset_param_t> interp (env);
 
-      parsed_charstrings[i].alloc (str.length / 2);
+      parsed_charstrings[i].alloc (str.length);
       subr_subset_param_t  param (&parsed_charstrings[i],
                                   &parsed_global_subrs_storage,
                                   &parsed_local_subrs_storage[fd],