Summary
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Allow `SuppressWarnings` annotation to be used in package declarations.

Problem
-------
While allowed to be used on type and module declarations, among other targets, `SuppressWarnings` annotations cannot be used on package declarations.

Solution
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Include `PACKAGE` in the set of declared targets for `SuppressWarnings`.

Note: while the SuppressWarnings annotation does have a JLS section (9.6.4.5. @SuppressWarnings), the section doesn't mention the target list therefore doesn't appear to need to be updated.

Specification
-------------

    diff --git a/src/java.base/share/classes/java/lang/SuppressWarnings.java b/src/java.base/share/classes/java/lang/SuppressWarnings.java
    index 09ab6c4724b..726d67deece 100644
    --- a/src/java.base/share/classes/java/lang/SuppressWarnings.java
    +++ b/src/java.base/share/classes/java/lang/SuppressWarnings.java
    @@ -38,6 +38,9 @@ import static java.lang.annotation.ElementType.*;
      * However, note that if a warning is suppressed in a {@code
      * module-info} file, the suppression applies to elements within the
      * file and <em>not</em> to types contained within the module.
    + * Likewise, if a warning is suppressed in a {@code
    + * package-info} file, the suppression applies to elements within the
    + * file and <em>not</em> to types contained within the package.
      *
      * <p>As a matter of style, programmers should always use this annotation
      * on the most deeply nested element where it is effective.  If you want to
    @@ -52,7 +55,7 @@ import static java.lang.annotation.ElementType.*;
      * @jls 5.5 Casting Contexts
      * @jls 9.6.4.5 @SuppressWarnings
      */
    -@Target({TYPE, FIELD, METHOD, PARAMETER, CONSTRUCTOR, LOCAL_VARIABLE, MODULE})
    +@Target({TYPE, FIELD, METHOD, PARAMETER, CONSTRUCTOR, LOCAL_VARIABLE, PACKAGE, MODULE})
     @Retention(RetentionPolicy.SOURCE)
     public @interface SuppressWarnings {
         /**