merge revision(s) 40334: [Backport #8149]

	* iseq.c (iseq_location_setup): re-use existing string when iseq has
	  the same path and absolute_path. [Bug #8149]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@42089 b2dd03c8-39d4-4d8f-98ff-823fe69b080e