merge revision(s) 39718: [Backport #8001] [Backport #8023]

	* Merge Onigmo d4bad41e16e3eccd97ccce6f1f96712e557c4518.
	  fix lookbehind assertion fails with /m mode enabled. [Bug #8023]
	  fix \Z matches where it shouldn't. [Bug #8001]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@40088 b2dd03c8-39d4-4d8f-98ff-823fe69b080e