Miscellaneous rebar3 fixes

Correct Makefile clean targets

Fix a few more include() -> include_lib() for depedency includes

Use project_app_dirs to reference elixir app from rebar3 (lib_dirs is
no longer supported)

Makefile.in

@@ -334,8 +334,8 @@ uninstall-all: uninstall-binary
 	rm -rf $(LOGDIR)
 
 clean:
-	rm -rf deps/.got
-	rm -rf deps/.built
+	rm -rf $(DEPSDIR)/.got
+	rm -rf $(DEPSDIR)/.built
 	rm -rf test/*.beam
 	$(REBAR) clean
 
@@ -346,8 +346,8 @@ distclean: clean clean-rel
 	rm -f config.status
 	rm -f config.log
 	rm -rf autom4te.cache
-	rm -rf deps
-	rm -rf ebin
+	rm -rf $(EBINDIR)
+	rm -rf $(DEPSBASE)
 	rm -f Makefile
 	rm -f vars.config
 	rm -f src/ejabberd.app.src

rebar.config

@@ -121,7 +121,7 @@
                           ]}}.
 
 {if_rebar3, {if_var_true, elixir,
-              {lib_dirs, ["_build/default/lib/elixir/lib"]}}}.
+              {project_app_dirs, [".", "elixir/lib"]}}}.
 {if_not_rebar3, {if_var_true, elixir,
               {lib_dirs, ["deps/elixir/lib"]}}}.
 {if_var_true, elixir,
@@ -149,10 +149,7 @@
                    {if_var_false, zlib, "(\"ezlib\":_/_)"}]}.
 
 {eunit_compile_opts, [{i, "tools"},
-                      {i, "include"},
-                      {i, "deps/fast_xml/include"},
-                      {i, "deps/p1_utils/include"},
-                      {i, "deps/xmpp/include"}]}.
+                      {i, "include"}]}.
 
 {cover_enabled, true}.
 {cover_export_enabled, true}.

test/muc_tests.erl

@@ -31,7 +31,6 @@
 		disconnect/1, put_event/2, get_event/1, peer_muc_jid/1,
 		my_muc_jid/1, get_features/2, set_opt/3]).
 -include("suite.hrl").
--include("jid.hrl").
 
 %%%===================================================================
 %%% API

test/suite.hrl

@@ -1,8 +1,9 @@
 -include_lib("common_test/include/ct.hrl").
 -include_lib("fast_xml/include/fxml.hrl").
--include("ns.hrl").
+-include_lib("xmpp/include/jid.hrl").
+-include_lib("xmpp/include/ns.hrl").
+-include_lib("xmpp/include/xmpp_codec.hrl").
 -include("mod_proxy65.hrl").
--include("xmpp_codec.hrl").
 
 -define(STREAM_TRAILER, <<"</stream:stream>">>).