2008-01-25	Timo Bingmann
	* btree.h: Fixed a valgrind-detected bug based on a new test case
	received via email. During the find() function find_lower() is
	called and returns the slot number with the smallest or equal
	key. However if the queried key is larger than all keys in a leaf
	node or in the whole tree, find_lower() returns a slot number past
	the last valid key slot. Comparison of this invalid slot with the
	queried key then yields an uninitialized memory error in valgrind.

2007-05-12	Timo Bingmann
	* btree.h: Fixed segfault in print() because of non-existing root.
		   Fixed segfault in end() when the tree is totally empty.
		   Added BTREE_FRIENDS macro so that wxBTreeDemo can
		   access private members.
		   Changing print function to output to a user-given
		   std::ostream