Refine specification of javax.lang.model.element.Modifier::toString

Summary

Define the behavior of javax.lang.model.element.Modifier::toString in terms of modifier names in the JLS.

Problem

Clarifies a situation where the name of the enum constant and the name in the JLS don't just differ by upper/lower case, as for non-sealed.

Solution

Change to the spec to be defined in terms of JLS names.

Specification

      /**
-     * Returns this modifier's name in lowercase.
+     * Returns this modifier's name as defined in <cite>The
+     * Java&trade; Language Specification</cite>.
+     * The modifier name is the {@linkplain #name() name of the enum
+     * constant} in lowercase and with any underscores ("{@code _}")
+     * replaced with hyphens ("{@code -}").
      */
     public String toString() {