Fix: avl_get_hash() should get a const param
Fix: avl_height() should get const arg
Fix: avl_node_cnt() should get const arg
Merge pull request #236 from matthiasbeyer/fix-const_args_avl

Made some avl function parameters const
Add implementation for r_set_equal()
Added ll_equal() implementation
[WIP] Started implementation for avl_equal()
Started implementation for ht_equal()
Added missing entries in CMakeLists file