drd: Avoid that optimized strlen() implementations trigger false positive race reports (#326091)


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13664 a5019735-40e9-0310-863c-91ae7b9d1cf9
NEWS: Add entry for bug #326091 (drd and __GI_strlen())

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13665 a5019735-40e9-0310-863c-91ae7b9d1cf9