Add sun.misc annotation marker

This commit adds an annotation that should be used to mark any usage of
the `sun.misc` API.

spring-core/src/main/java/org/springframework/lang/UsesSunMisc.java

@@ -0,0 +1,20 @@
+package org.springframework.lang;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Indicates that the annotated element uses an API from the {@code sun.misc}
+ * package.
+ *
+ * @author Stephane Nicoll
+ * @since 4.3
+ */
+@Retention(RetentionPolicy.CLASS)
+@Target({ElementType.METHOD, ElementType.CONSTRUCTOR, ElementType.TYPE})
+@Documented
+public @interface UsesSunMisc {
+}