Feature/mbedtls (#84)

* try to import mbedtls and build it

* add stubs socket class

* some boilterplate, read and write function implemented

* more boilterplate / current error in handshake because no CA cert is setup

* add something so skip ca verification, can ws curl https://google.com !

* cleanup / close implemented

* tweak CMakefiles

* typo in include

* update readme

* disable unittests

third_party/mbedtls/crypto/doxygen/input/doc_rng.h

@@ -0,0 +1,46 @@
+/**
+ * \file doc_rng.h
+ *
+ * \brief Random number generator (RNG) module documentation file.
+ */
+/*
+ *
+ *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
+ *  SPDX-License-Identifier: Apache-2.0
+ *
+ *  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.
+ *
+ *  This file is part of mbed TLS (https://tls.mbed.org)
+ */
+
+/**
+ * @addtogroup rng_module Random number generator (RNG) module
+ *
+ * The Random number generator (RNG) module provides random number
+ * generation, see \c mbedtls_ctr_drbg_random().
+ *
+ * The block-cipher counter-mode based deterministic random
+ * bit generator (CTR_DBRG) as specified in NIST SP800-90. It needs an external
+ * source of entropy. For these purposes \c mbedtls_entropy_func() can be used.
+ * This is an implementation based on a simple entropy accumulator design.
+ *
+ * The other number generator that is included is less strong and uses the
+ * HAVEGE (HArdware Volatile Entropy Gathering and Expansion) software heuristic
+ * which considered unsafe for primary usage, but provides additional random
+ * to the entropy pool if enables.
+ *
+ * Meaning that there seems to be no practical algorithm that can guess
+ * the next bit with a probability larger than 1/2 in an output sequence.
+ *
+ * This module can be used to generate random numbers.
+ */