This commit changes nghttpx's mruby script handling. Previously we
have 2 options to specify the mruby script file to be run on request
and on response. Now they are merged into 1 option, namely
--mruby-file. It now must return object. On request, the object's
on_req(env) method is invoked with env object. Similarly, on
response, the object's on_resp(env) method is invoked. The
specification of Env object has not changed.
In reverse proxy usage, backend server most likely wants to see the
original header field. So this commit turns off host header rewrite
by default. --no-host-rewrite option is deprecated, and if it is
used, warning message is displayed. --host-rewrite option is added to
enable host rewrite.
Tatsuhiro Tsujikawa
Lucas Pardue
Peeyush Aggarwal