tree.h: drop duplicated content of tree.h

Introduced in 9859bc783adcd51729b3d7563902ac8caca67b42
("r15764@tombo:  nickm | 2007-12-31 15:46:16 -0500")
Merge pull request #125 from azat/tree.h-drop-copy

tree.h: drop duplicated content of tree.h