Searches a GTree using search_func.
The search_func is called with a pointer to the key of a key/value
pair in the tree, and the passed in user_data. If search_func returns
0 for a key/value pair, then the corresponding value is returned as
the result of g_tree_search(). If search_func returns -1, searching
will proceed among the key/value pairs that have a smaller key; if
search_func returns 1, searching will proceed among the key/value
pairs that have a larger key.
Searches a GTree using search_func. The search_func is called with a pointer to the key of a key/value pair in the tree, and the passed in user_data. If search_func returns 0 for a key/value pair, then the corresponding value is returned as the result of g_tree_search(). If search_func returns -1, searching will proceed among the key/value pairs that have a smaller key; if search_func returns 1, searching will proceed among the key/value pairs that have a larger key.