mbedtls: configurable options for controlling dynamic memory allocations

Modifies https://github.com/espressif/esp-idf/pull/2237

components/mbedtls/port/include/esp_mem.h

@@ -0,0 +1,20 @@
+// Copyright 2018 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#pragma once
+
+#include <stdlib.h>
+
+void *esp_mbedtls_mem_calloc(size_t n, size_t size);
+void esp_mbedtls_mem_free(void *ptr);