splay-tree.c (splay_tree_xmalloc_allocate, [...]): Use K&R-style definitions, not prototyped definitions.

* splay-tree.c (splay_tree_xmalloc_allocate,
splay_tree_xmalloc_deallocate): Use K&R-style definitions, not
prototyped definitions.  Mark `data' arguments as unused.

From-SVN: r50384