Fix key addition in FSFS repositories with formats less than SVN_FS_FS__MIN_NO_GLOBAL_IDS_FORMAT.
Fix key addition in FSFS repositories with formats less than
SVN_FS_FS__MIN_NO_GLOBAL_IDS_FORMAT.

* subversion/libsvn_fs_fs/key-gen.c
  (svn_fs_fs__add_keys): Use signed type.

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