merge revision(s) 43376: [Backport #9038]

	* encoding.c (load_encoding): should preserve outer errinfo, so that
	  expected exception may not be lost.  [ruby-core:57949] [Bug #9038]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@43414 b2dd03c8-39d4-4d8f-98ff-823fe69b080e