trivial diff: fix spurious warnings for nested modules

[Fergus Henderson]

Estimated hours taken: 0.25

Avoid some spurious warning messages.

compiler/modules.m:
	Don't warn "module doesn't export anything"
	for modules which export only sub-modules.

Index: modules.m
===================================================================
RCS file: /home/mercury1/repository/mercury/compiler/modules.m,v
retrieving revision 1.67
diff -u -u -r1.67 modules.m
--- modules.m	1998/03/20 05:52:29	1.67
+++ modules.m	1998/04/30 07:15:09
@@ -768,7 +768,8 @@
 check_for_no_exports([Item - _Context | Items], ModuleName) -->
 	(
 		{ Item = nothing
-		; Item = module_defn(_,_)
+		; Item = module_defn(_, ModuleDefn),
+		  ModuleDefn \= include_module(_)
 		}
 	->
 		% nothing useful - keep searching
-- 
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