Remove no-longer-used svn_*_get_mergeinfo_for_tree APIs.

Remove no-longer-used svn_*_get_mergeinfo_for_tree APIs.

* subversion/include/private/svn_fs_mergeinfo.h
  (svn_fs_mergeinfo__get_mergeinfo): Remove.

* subversion/include/svn_fs.h
* subversion/libsvn_fs/fs-loader.c
  (svn_fs_get_mergeinfo_for_tree): Remove.

* subversion/libsvn_fs/fs-loader.h
  (struct root_vtable_t): Remove get_mergeinfo_for_tree.

* subversion/libsvn_fs_base/tree.c
  (root_vtable): Remove svn_fs_mergeinfo__get_mergeinfo_for_tree.

* subversion/libsvn_fs_fs/tree.c
  (collect_mergeinfo_for_tree, get_mergeinfo_hash_for_tree,
   fs_get_mergeinfo_for_tree): Remove.
  (root_vtable): Remove fs_get_mergeinfo_for_tree.

* subversion/libsvn_fs_util/mergeinfo-sqlite-index.c
  (parse_mergeinfo_from_db, get_mergeinfo_for_children,
   svn_fs_mergeinfo__get_mergeinfo_for_tree): Remove.

git-svn-id: http://svn.collab.net/repos/svn/trunk@29010 612f8ebc-c883-4be0-9ee0-a4e9ef946e3a