merge revision(s) 47820: [Backport #10330]

	* error.c: update exception tree. [DOC]
	  reported by @hemge via twitter.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@47932 b2dd03c8-39d4-4d8f-98ff-823fe69b080e