Fix integer overflow in stats of trees.

2018-01-12  Martin Liska  <mliska@suse.cz>

	* tree-core.h: Use uint64_t instead of int.
	* tree.c (tree_node_counts): Likewise.
	(tree_node_sizes): Likewise.
	(dump_tree_statistics): Use PRIu64 in printf format.

From-SVN: r256583