Ceph » rgw

- Make Lua scripting, the runtime- and the compiletime-dependency optional
- Introduce a compile-time flag for enabling/disabling it via the build system
- Make sure disabling Lua scripting automatically also disables Lua packages, but not vice versa
- Keep backwards-compatible defaults

The RGW supports executing Lua scripts on either the pre-request hook or the post-request hook.
Optionally, it can also support loading Lua packages in addition to what the Lua standart library supports
for use in these Lua scripts, but this feature must be enabled at compile time.
There are however also benefits to making the entire Lua scripting feature optional, enabled or disabled by compile time flags.
For one, the minimum requirements to build the RGW in any capacity shrink a bit. Also the runtime requirement of the Lua runtime
can be removed, if desired. In high-security environments, the Lua feature may be a problem and last but not least, reducing the
minimal requirements for building and developing ceph may help the community.