UnitKit: add @try{}/@catch{} block in -internalRunTest to make up for the fact that NSTimer on GNUstep catches and ignores exceptions

git-svn-id: http://svn.gna.org/svn/etoile/trunk/Etoile/Frameworks/UnitKit@10509 7b3f36aa-e6db-49c1-8b4c-66eac1997e64