8030048: (fs) Support UserDefinedFileAttributeView/extended attributes on OS X / HFS+

Reviewed-by: alanb

src/java.base/macosx/classes/sun/nio/fs/BsdFileSystem.java

@@ -56,6 +56,8 @@ class BsdFileSystem extends UnixFileSystem {
         private static Set<String> supportedFileAttributeViews() {
             Set<String> result = new HashSet<String>();
             result.addAll(standardFileAttributeViews());
+            // additional BSD-specific views
+            result.add("user");
             return Collections.unmodifiableSet(result);
         }
     }