Revert luerl from v0.4 which has a compilation warning; v0.3 is enough

Revert "Update luerl dependency from v0.3 to v0.4"

This reverts commit 64f3f3287a.

mix.exs

@@ -130,7 +130,7 @@ defmodule Ejabberd.Mixfile do
     for {:true, dep} <- [{config(:pam), {:epam, "~> 1.0"}},
                          {config(:redis), {:eredis, "~> 1.2.0"}},
                          {config(:zlib), {:ezlib, "~> 1.0"}},
-                         {config(:lua), {:luerl, "~> 0.4.0"}},
+                         {config(:lua), {:luerl, "~> 0.3.1"}},
                          {config(:sqlite), {:sqlite3, "~> 1.1"}}], do:
       dep
   end

rebar.config

@@ -41,7 +41,7 @@
         {jose, ".*", {git, "https://github.com/potatosalad/erlang-jose", {tag, "1.9.0"}}},
         {lager, ".*", {git, "https://github.com/erlang-lager/lager", {tag, "3.9.1"}}},
         {if_var_true, lua,
-         {luerl, ".*", {git, "https://github.com/rvirding/luerl", {tag, "v0.4"}}}},
+         {luerl, ".*", {git, "https://github.com/rvirding/luerl", {tag, "v0.3"}}}},
         {mqtree, ".*", {git, "https://github.com/processone/mqtree", {tag, "1.0.13"}}},
         {p1_acme, ".*", {git, "https://github.com/processone/p1_acme", {tag, "1.0.12"}}},
         {if_var_true, mysql,