Followup to r1461335: rename function and update its signature.

Notably, for FSFS a layer of indirection is removed: the tree.c implementation
is used directly without a fs_fs.c wrapper.

* subversion/include/svn_fs.h
  (svn_fs_verify_rev): Morph into..
  (svn_fs_verify_root): .. this.

* subversion/libsvn_fs/fs-loader.c
  (svn_fs_verify_rev, svn_fs_verify_root): Propagate.

* subversion/libsvn_fs/fs-loader.h
  (fs_vtable_t.verify_rev): Morph into ..
  (fs_vtable_t.verify_root): .. this.

* subversion/libsvn_fs_base/fs.c
  (base_bdb_verify_rev, base_bdb_verify_root): Propagate.

* subversion/libsvn_fs_fs/fs.c
  (fs_vtable): Propagate.

* subversion/libsvn_fs_fs/fs_fs.c
  (svn_fs_fs__verify_rev): Remove.
  
* subversion/libsvn_fs_fs/fs_fs.h
  (svn_fs_fs__verify_rev): Remove.

* subversion/libsvn_fs_fs/tree.c
  (svn_fs_fs__verify_root):
    Add here the important parts of svn_fs_fs__verify_rev() --- namely, the
    introductory comment.

* subversion/libsvn_repos/dump.c
  (svn_repos_verify_fs2): Propagate.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1461648 13f79535-47bb-0310-9956-ffa450edef68