def ext (func_name, key='', value='', opts={})

      @db.ext(func_name.to_s, key.to_s, value.to_s, compute_ext_opts(opts))
    end
def ext (func_name, key='', value='', opts={})

      @db.ext(func_name.to_s, key.to_s, value.to_s, compute_ext_opts(opts))
    end
Calls a lua embedded function
 (http://tokyocabinet.sourceforge.net/tyrantdoc/#luaext)

 Options are :global_locking and :record_locking

 Returns the return value of the called function.

 Nil is returned in case of failure.