merge revision(s) 41077,41105: [Backport #8485] [Backport #8500] [Backport #8578]

	* ext/date/date_core.c: fixed a bug [ruby-core:55295].  reported
	  by Riley Lynch.

	* ext/date/date_core.c: fixed coding error [ruby-core:55337].
	  reported by Riley Lynch.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@41952 b2dd03c8-39d4-4d8f-98ff-823fe69b080e