dnsdist: Add 'spoof' and 'spoofRaw' Lua bindings

[rgacogne]

This commits makes it possible to spoof multiple values from Lua:

function myfunc(dq)
  local ret = { newCA("192.0.2.1"), newCA("192.0.2.2") }
  dq:spoof(ret)
  return DNSAction.HeaderModify
end

addAction(AllRule(), LuaAction(myfunc))

Barely tested, need tests and documentation.
Now with documentation and tests courtesy of tjikkun, thanks a lot!

Short description

Checklist

I have:

• read the CONTRIBUTING.md document
• compiled this code
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)

[rgacogne]

It might be better to take a variant instead of having two functions, by the way.