Motivation:
When checking if a value is present, ReadOnlyHttp2Headers always ignores
case for values.
RFC 7540 says: https://tools.ietf.org/html/rfc7540#section-8.1.2
"header field names are strings of ASCII characters that are compared in a case-insensitive fashion"
But there is no such constraint on header values
Modifications:
Updated ReadOnlyHttp2Headers.contains to compare header value in a
case-sensitive way.
Result:
ReadOnlyHttp2Headers compares header names in a case-insensitive way,
values in a case-sensitive way.
7f23c34b55