intern.h: deprecate disable and enable super

* include/ruby/intern.h (rb_disable_super, rb_enable_super): warn
  as deprecated at build time, instead of ignoring silently or
  warning at runtime only.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48283 b2dd03c8-39d4-4d8f-98ff-823fe69b080e