[R-qtl/el6] (2 commits) ...replace macro with a list, needed for EL <= 6

[Dan Horák]

Summary of changes:

  c8e95f5... - Changed stack limit on ppc64 and s390x to allow checks to (*)
  1928610... replace macro with a list, needed for EL <= 6

(*) This commit already existed in another branch; no separate mail sent