Fix imports from objects

This almost reverts 345ecbf, since now properties are no longer created for
objects

compiler/frontend/src/org/jetbrains/jet/lang/resolve/Importer.java

@@ -148,7 +148,6 @@ public interface Importer {
 
         @Override
         public void addAliasImport(@NotNull DeclarationDescriptor descriptor, @NotNull Name aliasName) {
-            assert !DescriptorUtils.isSingleton(descriptor) : "Never import objects: " + descriptor;
             imports.add(new AliasImportEntry(descriptor, aliasName));
         }
 

compiler/frontend/src/org/jetbrains/jet/lang/resolve/QualifiedExpressionResolver.java

@@ -111,9 +111,7 @@ public class QualifiedExpressionResolver {
         }
 
         for (DeclarationDescriptor descriptor : descriptors) {
-            if (!DescriptorUtils.isSingleton(descriptor)) {
-                importer.addAliasImport(descriptor, aliasName);
-            }
+            importer.addAliasImport(descriptor, aliasName);
         }
 
         return descriptors;

compiler/testData/diagnostics/tests/scopes/ImportObjectAndUseAsSupertype.kt

@@ -12,7 +12,7 @@ package baz
 
 import foo.Bar
 
-class C: <!UNRESOLVED_REFERENCE!>Bar<!>
+class C: <!SUPERTYPE_NOT_INITIALIZED, FINAL_SUPERTYPE!>Bar<!>
 
 fun test() {
     Bar.bar()