[openresty] Added openresty build based upon nginx.

Added an openresty build definition. It should be a drop-in replacement
for standard nginx.

 - Since openresty is a metapackage, its configure script descends into
   the source files and calls `configure` for nginx. However, there is a
   bug. The nginx --with-ld-opts is comma-delimited, but the openresty
   `configure` generates a space-delimited list. A patch is included in
   Omnibus to fix this.

 - The sbin and nginx.conf had to be explicitly set to the omnibus
   convensions.

 - Openresty cookbook will automatically detect AIO capabilities and
   automatically enable AIO compile flags. It appears that Ubuntu 10.04
   have the necessary kernel version. However, this requires compiling
   additional AIO libraries. This is a possible improvement for future
   builds.