Fully debug rotations.

data_structures/avl_tree/src/avl_tree.c
	-Fix some incorrect statements in `_insert()`.
	-Move balance-setting from `_rotateLeft()`/`_rotateRight()` to
	`_insert()`, because it only applies to LL/RR rotations and not
	LR/RL rotations, and the latter two use those functions.