Fix Javadoc @Since checkstle violations

Apply consistent `@Since` tags and retrofit the existing code using a
best guess from the git history.

Closes gh-17360

spring-boot-tools/spring-boot-autoconfigure-processor/src/main/java/org/springframework/boot/autoconfigureprocessor/AutoConfigureAnnotationProcessor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2018 the original author or authors.
+ * Copyright 2012-2019 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.
@@ -47,6 +47,7 @@ import javax.tools.StandardLocation;
  *
  * @author Madhura Bhave
  * @author Phillip Webb
+ * @since 1.5.0
  */
 @SupportedAnnotationTypes({ "org.springframework.context.annotation.Configuration",
 		"org.springframework.boot.autoconfigure.condition.ConditionalOnClass",