faster to compile.

A small selection of packages was tested going from:

Executed in  696.30 secs   fish           external
   usr time   82.98 mins  395.00 micros   82.98 mins
   sys time    9.02 mins    0.00 micros    9.02 mins

to:

Executed in  592.20 secs   fish           external
   usr time   84.84 mins  361.00 micros   84.84 mins
   sys time    8.85 mins   57.00 micros    8.85 mins

Tested by running make -j 12 and wiping staging/build_dir/target_x

Signed-off-by: Rosen Penev <rosenp@gmail.com>

Switch to CMake. Allows faster compilation and simplification of the
Makefile.

Switched libwslay to a static InstallDev library. Allows further
simplification of the Makefile and a smaller size when used with h2o.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

Wslay is a WebSocket library written in C. It implements the protocol version 13
 described in RFC 6455. This library offers 2 levels of API: event-based API and
 frame-based low-level API. For event-based API, it is suitable for non-blocking
 reactor pattern style. You can set callbacks in various events. For frame-based
 API, you can send WebSocket frame directly. Wslay only supports data transfer
 part of WebSocket protocol and does not perform opening handshake in HTTP.

Signed-off-by: James Taylor <james@jtaylor.id.au>