New overloads of suite::expect take the file and line number
as individual parameters, cleaning up the file name output
by showing only the filename part (to not leak the full path,
which might contain sensitive information).
A new macro BEAST_EXPECTS allows an additional reason
string as well as reporting the file and line. Typical usage:
```
error_code ec;
...
if(! BEAST_EXPECTS(! ec, ec.message()))
return;
```
The log member is changed to derive from std::ostream. A new
class dstream is derived from std::ostream to support redirection
to the Visual Studio Output Window if a debugger is attached.
Obsolete classes abstract_ostream and its derived variants are
removed.
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
