Explicitly limit the dimensions of a star delta container which allows us
to cast sizes to 32 bits.

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

* subversion/libsvn_fs_x/reps.h
  (svn_fs_x__reps_add): Allow for error returns.

* subversion/libsvn_fs_x/reps.c
  (MAX_TEXT_BODY,
   MAX_INSTRUCTIONS): Formally declare dimensional limit to the star
                      delta container.
  (svn_fs_x__reps_add_base): Update caller. Explicitly cast index to 32 bits.
  (add_new_text): Explicitly cast length values to 32 bits. They have been
                  limited to < 2GB be the caller already.
  (svn_fs_x__reps_add): Make sure the container size stays within set limits.

* subversion/libsvn_fs_x/pack.c
  (write_reps_containers): Update caller.

* subversion/tests/libsvn_fs_x/fs-x-pack-test.c
  (test_reps): Same.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1616600 13f79535-47bb-0310-9956-ffa450edef68