Add xmerl to PLT_APPS for rabbit_common

Author: mkuratczyk

deps/rabbit_common/Makefile

@@ -43,7 +43,7 @@ DEP_EARLY_PLUGINS = $(PROJECT)/mk/rabbitmq-early-plugin.mk
 DEP_PLUGINS = $(PROJECT)/mk/rabbitmq-build.mk \
 	      $(PROJECT)/mk/rabbitmq-hexpm.mk
 
-PLT_APPS += mnesia crypto ssl
+PLT_APPS += mnesia crypto ssl xmerl
 
 include ../../rabbitmq-components.mk
 include ../../erlang.mk