basic_headers no longer combines fields with the same name by appending
a comma and concatenating the two values together. This was breaking
certain header fields which expect each value to be distinct, such as
the "Set-Cookie" header.
Now the container behaves more like a multi set with respect to insertion
of multiple values with the same field name. Additional member functions
are provided to provide extra functionality.
A new concept Parser is introduced with routines to read from a stream
into the parser. This solves a problem with the old read interface where
messages must be default constructible and move assignable.
Parser fixes:
* Fix detect invalid reason-phrase octets
* Fix write_eof to set the 'complete' state on success
* Fix consider parse complete if eof received on empty body
WebSocket:
* Increase coverage
Core:
* Test buffer_cat iterator move members
HTTP:
* Fixed yield / resume in writer
* Fixed message serialization with chunked encoding
* Test yield / resume in writer
* Test all conditional branches during message serialization
* Test chunked encoding
* Increase coverage on parse_error
* Add parse_error::general
WebSocket:
* Add error::general
* Increase coverage in error
* Don't include the test code in coverage reports
* Add test code for missing coverage
Other:
* Improve the README.md
* Fix warning in sha1_context
* Tidy up the examples use of namespaces
* Various fixes to documentation and javadocs
