MFC r315636,315876,316095:

MFC r315636,315876,316095:
Sync libarchive with vendor

Vendor changes/bugfixes (FreeBSD-related):
r315636:
  PR 867 (bsdcpio): show numeric uid/gid when names are not found
  PR 870 (seekable zip): accept files with valid ZIP64 EOCD headers
  PR 880 (pax): Fix handling of "size" pax header keyword
  PR 887 (crypto): Discard 3072 bytes instead of 1024 of first keystream
  OSS-Fuzz issue 806 (mtree): rework mtree_atol10 integer parser
  Break ACL read/write code into platform-specific source files

r315876:
  Store extended attributes with extattr_set_link() if no fd is provided
  Add extended attribute tests to libarchive and bsdtar
  Fix tar's test_option_acls
  Support the UF_HIDDEN file flag

r316095:
  Constify variables in several places
  Unify platform ACL code in a single source file
  Fix unused variable if compiling on FreeBSD without NFSv4 ACL support