Both connect_secure() and connect_unsecure() call connect_to_peer().
Prior to this commit spicec.log reported all connections as unsecure,
as connect_secure() called connect_unsecure() to make the connection.
This fixes RH bug #653545
Fixed since v1:
- don't include C code, rather use the common lib
- add missing spice_openssl_verify_free() call
- keep the extra-parsing of subject for error reporting
3 available mechanisms: by public key, by host name, and by certificate subject name.
In the former method, chain of trust verification is not performed.
The CA certificate files are looked for under <spice-config-dir>/spice_truststore.pem
windows <spice-config-dir>=%APPDATA%\spicec\
linux <spice-config-dir>=$HOME/.spicec/