Account for http experimental settings frame codes
Account for http experimental settings frame codes

As per https://tools.ietf.org/html/rfc7540#section-11.3, the http
settings frame parameter with code in the range 0xf000 to 0xffff
is reserved for experimental use.

A specific example is gRPC's "allow true binary metadata" experimental
optimization, which uses code 65027 and throws parse settings errors
with chatterbox.

See: https://github.com/grpc/grpc/blob/master/src/core/ext/transport/chttp2/transport/http2_settings.h#L34

joedevivo/chatterbox,joedevivo/chatterbox,rslota/chatterbox,tsloughter/chatterbox,tsloughter/chatterbox,rslota/chatterbox