Bump version to 6.14.2 (ruby#1387)

ruby/rdoc@v6.14.1...master but mostly for
ruby#1386 which can immediately improve `ruby/ruby`'s documentation.

Author: st0012

lib/rdoc/version.rb

@@ -5,6 +5,6 @@ module RDoc
   ##
   # RDoc version you are using
 
-  VERSION = '6.14.1'
+  VERSION = '6.14.2'
 
 end