Drop unused interface method

There was the only usage and it's redundant.
JetClass' implementation name is refined.

compiler/backend-common/src/org/jetbrains/kotlin/backend/common/DataClassMethodGenerator.java

@@ -79,8 +79,6 @@ public abstract class DataClassMethodGenerator {
     }
 
     private void generateComponentFunctionsForDataClasses() {
-        if (!declaration.hasPrimaryConstructor()) return;
-
         ConstructorDescriptor constructor = classDescriptor.getUnsubstitutedPrimaryConstructor();
         assert constructor != null : "Data class should have primary constructor";
 

compiler/frontend/src/org/jetbrains/kotlin/psi/JetClass.java

@@ -126,8 +126,7 @@ public class JetClass extends JetTypeParameterListOwnerStub<KotlinClassStub> imp
         return body.getAnonymousInitializers();
     }
 
-    @Override
-    public boolean hasPrimaryConstructor() {
+    private boolean hasExplicitPrimaryConstructor() {
         return getPrimaryConstructorParameterList() != null;
     }
 

compiler/frontend/src/org/jetbrains/kotlin/psi/JetClassOrObject.java

@@ -33,9 +33,6 @@ public interface JetClassOrObject extends PsiNameIdentifierOwner, JetDeclaration
     @NotNull
     List<JetClassInitializer> getAnonymousInitializers();
 
-    // Objects always "have" a primary constructor
-    boolean hasPrimaryConstructor();
-
     @Override
     @Nullable
     Name getNameAsName();

compiler/frontend/src/org/jetbrains/kotlin/psi/JetObjectDeclaration.java

@@ -122,11 +122,6 @@ public class JetObjectDeclaration extends JetNamedDeclarationStub<KotlinObjectSt
         return body.getAnonymousInitializers();
     }
 
-    @Override
-    public boolean hasPrimaryConstructor() {
-        return true;
-    }
-
     @Override
     public JetClassBody getBody() {
         return getStubOrPsiChild(JetStubElementTypes.CLASS_BODY);