Adds support for following TLS 1.3 extensions:
- PSKKeyExchangeModes
- SupportedVersions
- KeyShare
and uses them to implement newest Chrome and Firefox parrots.
Tests for default Golang uTLS were regenerated because
they previously used TLS-1.2 as max version.
The root cause of races is that global variables supportedSignatureAlgorithms and
cipherSuites are used both to form handshake and to check whether or not
peer responded with supported algorithm.
In this patch I create separate variables for this purpose.
Updated tests for kicks.
Finally, go fmt.
This function is not needed anymore, since check for whether ciphersuite is
supported is done against per-tls.Config, not against global variable.
One of needed changes for fixing data races, see #5
