JDK 13 RFR of JDK-8225353: Add @jls links to java.lang.Enum

[Joe Darcy]

Hello,

As noticed by Jon, the text for java.lang.Enum refers to a section of 
the JLS but does not use @jls tags:

"This is the common base class of all Java language enumeration types. 
More information about enums, including descriptions of the implicitly 
declared methods synthesized by the compiler, can be found in section 
8.9 of The Java™ Language Specification."

The javadoc for Enum would be improved if augmented by @jls to 
particular sections.

Please review the patch below to do this.

Thanks,

-Joe

diff -r 481999e74cea src/java.base/share/classes/java/lang/Enum.java
--- a/src/java.base/share/classes/java/lang/Enum.java Wed Jun 05 
08:24:03 2019 -0700
+++ b/src/java.base/share/classes/java/lang/Enum.java Wed Jun 05 
09:44:47 2019 -0700
@@ -59,6 +59,8 @@
   * @see     Class#getEnumConstants()
   * @see     java.util.EnumSet
   * @see     java.util.EnumMap
+ * @jls 8.9 Enum Types
+ * @jls 8.9.3 Enum Members
   * @since   1.5
   */