Important core bug fix, optional moved out of details namespace

Low level

• optional moved out of details namespace, tiny fix in optional

Bugs fixed

• When setting socket options to 1, they were set to uninitialized value instead. Worked because luck plus true = anything non-zero.

Better HTTP, WebSockets

Low level

• Experimental TLS code (not for use in a wild yet)
• Simple crab::optional for using older C++ standard
• Random is adapted to std containers

HTTP

• Streaming of HTTP bodies (both upload and download)
• New HTTP URI parser by AK

Bugs fixed

• WebSockets now support control frames between message chunks

Incompatible changes

• New callbacks design for WebSockets and postponing normal HTTP responses
• Stricter integer parser might break existing products

2 new impls (libev, CFRunLoop), PCG32 random, improved HTTP parsers, some fixes

Low level

• New expeimental low-level implementation added, CRAB_IMPL_LIBEV over libev (requires sudo apt install libev-dev).
• CFRunLoop low-level implementaion merged (partial support for TLS for now, full support is expected in near future).
• crab::Random now uses PCG32 instead of std::mt19337. Slow construction and number generation of std::mt19337 consumed too much CPU for lots of very short Web Messages.

HTTP

• To avoid some NATs disconnecting Web Sockets, OPCODE_PING is sent every 45 seconds (Timeout selected to be a bit less than TCP keepalive, which is 50 seconds for major browsers)
• New HTTP Query parser by AK
• New HTTP Cookie parser by AK

Bugs fixed

• HTTP socket shutdown was performed incorrectly for some HTTP/1.0 clients

Incompatible API changes

• sha1 and base64 moved into crab namespace