def deprecated(progname, &block)
      meta = Proc.new { "DEPRECATED: #{yield}" }
      add(LEVELS.index("WARN"), progname, &meta)
    end
def deprecated(progname, &block)
      meta = Proc.new { "DEPRECATED: #{yield}" }
      add(LEVELS.index("WARN"), progname, &meta)
    end
Print a deprecation warning. This actually outputs to +WARN+, but is
 prefixed with the string "DEPRECATED" first.

 @see (Logger#add)