Add a deprecated_in variable to util.deprecate args table (#1586)

lib/awful/util.lua

@@ -40,8 +40,16 @@ local displayed_deprecations = {}
 -- @param[opt] see The message to a new method / function to use.
 -- @tparam table args Extra arguments
 -- @tparam boolean args.raw Print the message as-is without the automatic context
+-- @tparam integer args.deprecated_in Print the message only when Awesome's
+--   version is equal to or greater than deprecated_in.
 function util.deprecate(see, args)
     args = args or {}
+    if args.deprecated_in then
+        local dep_ver = "v" .. tostring(args.deprecated_in)
+        if awesome.version < dep_ver then
+            return
+        end
+    end
     local tb = debug.traceback()
     if displayed_deprecations[tb] then
         return