Update mbedtls to 2.5.1 (#3964)

* Renaming changes:
  * macro prefix "POLARSSL" -> "MBEDTLS"
  * functions now prefixed with "mbedtls_"
  * rename PolarSSL++ -> mbedTLS++
  * rename polarssl submodule

* Use mbedtls' AES-CFB8 implementation.

* Add cSslConfig to wrap mbedtls_ssl_config

* Update cTCPLink and cBlockingSslClientSocket to use cSslConfig

* Use cSslConfig in cHTTPServer

* Use cSslConfig for cMojangAPI::SecureRequest

* CI Fixes

* Set -fomit-frame-pointer on the right target

src/mbedTLS++/CallbackSslContext.cpp

@@ -0,0 +1,60 @@
+
+// CallbackSslContext.cpp
+
+// Declares the cCallbackSslContext class representing a SSL context wrapper that uses callbacks to read and write SSL peer data
+
+#include "Globals.h"
+#include "CallbackSslContext.h"
+
+
+
+
+
+
+cCallbackSslContext::cCallbackSslContext(void) :
+	m_Callbacks(nullptr)
+{
+	// Nothing needed, but the constructor needs to exist so
+}
+
+
+
+
+
+cCallbackSslContext::cCallbackSslContext(cCallbackSslContext::cDataCallbacks & a_Callbacks) :
+	m_Callbacks(&a_Callbacks)
+{
+}
+
+
+
+
+
+int cCallbackSslContext::ReceiveEncrypted(unsigned char * a_Buffer, size_t a_NumBytes)
+{
+	if (m_Callbacks == nullptr)
+	{
+		LOGWARNING("SSL: Trying to receive data with no callbacks, aborting.");
+		return MBEDTLS_ERR_NET_RECV_FAILED;
+	}
+	return m_Callbacks->ReceiveEncrypted(a_Buffer, a_NumBytes);
+}
+
+
+
+
+
+int cCallbackSslContext::SendEncrypted(const unsigned char * a_Buffer, size_t a_NumBytes)
+{
+	if (m_Callbacks == nullptr)
+	{
+		LOGWARNING("SSL: Trying to send data with no callbacks, aborting.");
+		return MBEDTLS_ERR_NET_SEND_FAILED;
+	}
+	return m_Callbacks->SendEncrypted(a_Buffer, a_NumBytes);
+}
+
+
+
+
+