describe RbConfig.ruby.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@26245 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

NEWS

@@ -257,6 +257,10 @@ with all sufficient information, see the ChangeLog file.
   * new methods:
     * Zlib::GzipFile#path
 
+* rbconfig
+  * new methods:
+    * RbConfig.ruby
+
 === Language changes
 
 * Regexp properties (\p{}) names now ignore underscores, spaces, and case, so