merge revision(s) 41871: [Backport #8608]

	* ext/date/date_parse.c (date_zone_to_diff): [ruby-core:55831].


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@41951 b2dd03c8-39d4-4d8f-98ff-823fe69b080e