Use GNUtls because it is GPL compatible and instead of mbedTLS seems
to have a working non-blocking I/O integration. GNUtls has various
issues that could not be resolved easily:
* Pick spdy as sub protocol
* gmt_time not randomized
* private key loaded to RAM (but not verified)
This is the beginning and not the end. Client support might need more
work with actual tls verification. Maybe more manual x509 cert
verification is needed and maybe client certs don't work at all. I try
to ignore renegotiation as I threw away the key.
Reload x509 creds and keys as they might have changed from one
connection to another.
Change-Id: I9128e14084da1fc2705f858393f98b8133996172
Max