Fix infinite recursion bug in nested @Configuration

Prior to this commit, an infinite recursion would occur if a
@Configuration class were nested within its superclass, e.g.

  abstract class Parent {
      @Configuration
      static class Child extends Parent { ... }
  }

This is because the processing of the nested class automatically
checks the superclass hierarchy for certain reasons, and each
superclass is in turn checked for nested @Configuration classes.

The ConfigurationClassParser implementation now prevents this by
keeping track of known superclasses, i.e. once a superclass has been
processed, it is never again checked for nested classes, etc.

Issue: SPR-8955

org.springframework.context/src/test/java/org/springframework/context/annotation/configuration/spr8955/Spr8955Parent.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2002-2012 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.context.annotation.configuration.spr8955;
+
+import org.springframework.stereotype.Component;
+
+/**
+ * @author Chris Beams
+ * @author Willem Dekker
+ */
+abstract class Spr8955Parent {
+
+	@Component
+	static class Spr8955Child extends Spr8955Parent {
+
+	}
+
+}

org.springframework.context/src/test/java/org/springframework/context/annotation/configuration/spr8955/Spr8955Tests.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2002-2012 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.context.annotation.configuration.spr8955;
+
+import org.junit.Test;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+
+
+/**
+ * @author Chris Beams
+ * @author Willem Dekker
+ */
+public class Spr8955Tests {
+
+	@Test
+	public void repro() {
+		AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
+		ctx.scan("org.springframework.context.annotation.configuration.spr8955");
+		ctx.refresh();
+	}
+
+}