add clang sanitizers

@mortenvp, I've added the clang sanitizers.
I don't know in which version of clang they are available though (however they should be there in clang 3.5). And we don't have any buildslaves with a clang version higher than 3.3. Archlinux does however provide 3.4.1: https://www.archlinux.org/packages/?sort=&q=clang&maintainer=&flagged=

Also one more sanitizer exists (still work in progress though) maybe we should use that as well some day: http://clang.llvm.org/docs/DataFlowSanitizer.html