* include/ruby/ruby.h: prefix RUBY or RB to global symbols to get
  rid of name conflicts with other headers.
* include/ruby/encoding.h, include/ruby/intern.h: ditto.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51851 b2dd03c8-39d4-4d8f-98ff-823fe69b080e