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-identifiers.sh

@@ -0,0 +1,62 @@
+#!/bin/bash
+#
+# Create a file named identifiers containing identifiers from internal header
+# files or all header files, based on --internal flag.
+# Outputs the line count of the file to stdout.
+#
+# Usage: list-identifiers.sh [ -i | --internal ]
+
+set -eu
+
+if [ -d include/mbedtls ]; then :; else
+    echo "$0: must be run from root" >&2
+    exit 1
+fi
+
+INTERNAL=""
+
+until [ -z "${1-}" ]
+do
+  case "$1" in
+    -i|--internal)
+      INTERNAL="1"
+      ;;
+    *)
+      # print error
+      echo "Unknown argument: '$1'"
+      exit 1
+      ;;
+  esac
+  shift
+done
+
+if [ $INTERNAL ]
+then
+    HEADERS=$( ls include/mbedtls/*_internal.h library/*.h | egrep -v 'compat-1\.3\.h|bn_mul' )
+else
+    HEADERS=$( ls include/mbedtls/*.h include/psa/*.h library/*.h | egrep -v 'compat-1\.3\.h|bn_mul' )
+fi
+
+rm -f identifiers
+
+grep '^[^ /#{]' $HEADERS | \
+    sed -e 's/^[^:]*://' | \
+    egrep -v '^(extern "C"|(typedef )?(struct|enum)( {)?$|};?$)' \
+    > _decls
+
+if true; then
+sed -n -e 's/.* \**\([a-zA-Z_][a-zA-Z0-9_]*\)(.*/\1/p' \
+       -e 's/.*(\*\(.*\))(.*/\1/p' _decls
+grep -v '(' _decls | sed -e 's/\([a-zA-Z0-9_]*\)[;[].*/\1/' -e 's/.* \**//'
+fi > _identifiers
+
+if [ $( wc -l < _identifiers ) -eq $( wc -l < _decls ) ]; then
+    rm _decls
+    egrep -v '^(u?int(16|32|64)_t)$' _identifiers | sort > identifiers
+    rm _identifiers
+else
+    echo "$0: oops, lost some identifiers" 2>&1
+    exit 1
+fi
+
+wc -l identifiers