object.c: no TypeError at Symbol

	* object.c (special_object_p): uninterned Symbol also should not
	  raise a TypeError but return itself instead, as well as interned
	  Symbols.  [ruby-core:79216] [Bug #13145]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_4@57869 b2dd03c8-39d4-4d8f-98ff-823fe69b080e