add missing import


git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/libs/performance/trunk@38197 72102866-910b-0410-8b05-ffd578937521
tweaks for osx


git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/libs/performance/trunk@38198 72102866-910b-0410-8b05-ffd578937521