Can't require "http.util" from inside of openresty

[daurnimator]

Due to use of coroutine.wrap at module load time. See openresty/lua-nginx-module#1292

[daurnimator]

I guess we could skip the feature check if luajit is in use (via presence of jit global + jit.version_num?)

Or should it only special case the presence of ngx global? ==> What if someone is mocking an ngx environment with lua-http?