drd: Make the code added in r13792 portable

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13794 a5019735-40e9-0310-863c-91ae7b9d1cf9
Fix typo in poll wrapper

Patch from Ivo Raisr via BZ#330941


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13795 a5019735-40e9-0310-863c-91ae7b9d1cf9
Update NEWS for VEX r2814


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13796 a5019735-40e9-0310-863c-91ae7b9d1cf9