fsfs:  add a missing format check and some assertions.
fsfs:  add a missing format check and some assertions.

* subversion/libsvn_fs_fs/fs_fs.c
  (svn_fs_fs__revision_proplist):
    Check for SVN_FS_FS__MIN_PACKED_REVPROP_FORMAT.
  (update_min_unpacked_rev, update_min_unpacked_revprop):
    Assert that the relevant kind of packing is supported by the
    format.
  (svn_fs_fs__path_rev_absolute):
    Add an early exit for the "Packing not supported by the
    format" case.  It makes the code clearer.

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