Fix a bug which caused misleading error messages when

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Branches: main

Fix a bug which caused misleading error messages when
the module qualifier for an undefined symbol matched a
module imported only by ancestor modules.

compiler/make_hlds.m:
	Add modules imported by ancestor modules to the list
	of imported modules.

compiler/modules.m:
compiler/prog_data.m:
compiler/hlds_pred.m:
compiler/*.m:
	Record which items are imported from ancestor modules.

	Reorder the arguments of `modules__append_pseudo_decl'
	to make it easier to use with state variables.

	Use state variable syntax in `modules__grab_imported_modules'.

compiler/hlds_module.m:
	Remove an XXX comment documenting this bug.

configure.in:
	Check for state variable syntax when checking whether
	the compiler is up-to-date.

tests/invalid/Mmakefile:
tests/invalid/import_in_parent.{m,err_exp}:
	Test case.

compiler/prog_data.m

@@ -966,13 +966,13 @@
 		% such items need to be exported to the
 		% sub-modules.
 
-	;	imported(section)
+	;	imported(import_locn)
 		% This is used internally by the compiler,
 		% to identify declarations which originally
 		% came from some other module imported with 
 		% a `:- import_module' declaration, and which
 		% section the module was imported.
-	;	used(section)
+	;	used(import_locn)
 		% This is used internally by the compiler,
 		% to identify declarations which originally
 		% came from some other module and for which
@@ -1014,6 +1014,11 @@
 	--->	implementation
 	;	interface.
 
+:- type import_locn
+	--->	implementation
+	;	interface
+	;	ancestor.
+
 :- type sym_list	
 	--->	sym(list(sym_specifier))
 	;	pred(list(pred_specifier))