The union used to make a lot of sense to save space between
mutually exclusive modes.  But the fact the http2 struct
contains the http1 struct as well as it appearing in the
union means the http1 struct belongs outside the union.

This patch

 - eliminates the union
 - puts the http_related struct directly in struct lws
 - removes http_related from h2
 - puts h2 directly in struct lws if enabled for build
 - changes ws to be a pointer, allocated if we upgrade to ws
   (the ws part contains a 135 byte char array for ping / close)


Again all of this is entirely private / internal and doesn't affect
any apis.