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/tests/scripts/list-macros.sh

@@ -0,0 +1,23 @@
+#!/bin/sh
+
+set -eu
+
+if [ -d include/mbedtls ]; then :; else
+    echo "$0: must be run from root" >&2
+    exit 1
+fi
+
+HEADERS=$( ls include/mbedtls/*.h include/psa/*.h | egrep -v 'compat-1\.3\.h' )
+
+# White-list macros we want to be able to refer to that don't exist in the
+# crypto library, useful when referring to macros in Mbed TLS from comments.
+WHITELIST='MBEDTLS_ERR_SSL_CRYPTO_IN_PROGRESS'
+
+# Generate a list of macros and combine it with the white-listed macros in
+# sorted order.
+{ sed -n -e 's/.*#define \([a-zA-Z0-9_]*\).*/\1/p' $HEADERS |
+  egrep -v '^(asm|inline|EMIT|_CRT_SECURE_NO_DEPRECATE)$|^MULADDC_';
+  printf '%s\n' $WHITELIST;
+} | sort -u > macros
+
+wc -l macros