AnnotatedBeanDefinitionReader should respect @Fallback qualifier analogous to @Primary

Also add tests to cover qualifier classes.

spring-context/src/main/java/org/springframework/context/annotation/AnnotatedBeanDefinitionReader.java

@@ -43,6 +43,7 @@ import org.springframework.util.Assert;
  * @author Chris Beams
  * @author Sam Brannen
  * @author Phillip Webb
+ * @author Yanming Zhou
  * @since 3.0
  * @see AnnotationConfigApplicationContext#register
  */
@@ -266,6 +267,9 @@ public class AnnotatedBeanDefinitionReader {
 				if (Primary.class == qualifier) {
 					abd.setPrimary(true);
 				}
+				else if (Fallback.class == qualifier) {
+					abd.setFallback(true);
+				}
 				else if (Lazy.class == qualifier) {
 					abd.setLazyInit(true);
 				}