On the revprop-caching-ng branch:  Follow-up to r1620224. Missing changes.

* subversion/include/svn_error_codes.h
  (SVN_ERR_FS_INVALID_GENERATION): Declare new error code.

* subversion/tests/cmdline/svnadmin_tests.py
  (check_hotcopy_fsfs_fsx): Ignore the checksum when checking for revprop
                            generation 0.


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/revprop-caching-ng@1620235 13f79535-47bb-0310-9956-ffa450edef68