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/tests/data_files/dir-maxpath/long.sh

@@ -0,0 +1,35 @@
+#!/bin/sh
+
+set -eu
+
+: ${OPENSSL:=openssl}
+NB=20
+
+OPT="-days 3653 -sha256"
+
+# generate self-signed root
+$OPENSSL ecparam -name prime256v1 -genkey -out 00.key
+$OPENSSL req -new -x509 -subj "/C=UK/O=mbed TLS/CN=CA00" $OPT \
+             -key 00.key -out 00.crt
+
+# cXX.pem is the chain starting at XX
+cp 00.crt c00.pem
+
+# generate long chain
+i=1
+while [ $i -le $NB ]; do
+    UP=$( printf "%02d" $((i-1)) )
+    ME=$( printf "%02d" $i )
+
+    $OPENSSL ecparam -name prime256v1 -genkey -out ${ME}.key
+    $OPENSSL req -new -subj "/C=UK/O=mbed TLS/CN=CA${ME}" \
+                 -key ${ME}.key -out ${ME}.csr
+    $OPENSSL x509 -req -CA ${UP}.crt -CAkey ${UP}.key -set_serial 1 $OPT \
+                  -extfile int.opensslconf -extensions int \
+                  -in ${ME}.csr -out ${ME}.crt
+
+    cat ${ME}.crt c${UP}.pem > c${ME}.pem
+
+    rm ${ME}.csr
+    i=$((i+1))
+done