Port the BDB backend change from r926151 to the FSFS backend, also.
Port the BDB backend change from r926151 to the FSFS backend, also.

* subversion/libsvn_fs_fs/fs_fs.c
  (fold_change): Protect against another form of invalid sequence,
    where an 'add' follows other non-delete/reset changes on the same
    node.

Suggested by: glasser

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion