Enable more xref checks while still avoiding exports_not_used

rebar.config

@@ -31,4 +31,9 @@
     warn_export_all
 ]}.
 
-{xref_checks, [undefined_function_calls]}.
+{xref_checks,[
+    %% enable most checks, but avoid 'unused calls' which is often
+    %% very verbose
+    undefined_function_calls, undefined_functions, locals_not_used,
+    deprecated_function_calls, deprecated_functions, deprecated_functions
+]}.