Moved: ll.{c,h} -> ll/ll.{c,h}
Moved: avl.{c,h} -> avl/avl.{c,h}
Moved: ht.{c,h} -> ht/ht.{c,h}
Move: ll.c -> base.c
Move: avl.c -> base.c
Move: ht.c -> base.c
Outsourced: avl helper functions to common.{c,h}
Outsourced: avl_el type from avl.h to element.h
Fix: avl include base.c