[sagemath/f20] (4 commits) ...Update to sagemath 5.13

[pcpa]

Summary of changes:

  1d1576c... Rebuild for libgap 4.7.2. (*)
  64b1636... Adapt gap BRs to new gap subpackage structure. (*)
  b0cc814... Also adapt Requires to the new gap subpackage structure. (*)
  d0a2caf... Update to sagemath 5.13

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