Fix: Additional indent = 2
Fix: run astyle on avl/common.c
Merge pull request #205 from matthiasbeyer/fix-conditional_indent_astyle

The conditional indent setting for astyle was wrong
Destroy the linked list before removing the node
This fixes the double free on certain glibc vers.
Fix: on a _find() operation, the compare data element should be const
Fix: config is constant
Replace manual linked list loop with ll_find() call
Merge pull request #209 from TheNeikos/fix-avl_destroy

Fixes the double free on certain glibc vers.
Merge pull request #207 from matthiasbeyer/fix-ll_clearing_on_del

Fix: Destroy the linked list before removing the node
Merge pull request #208 from matthiasbeyer/fix-avl_use_ll_find

Fix: Use ll_find() in avl_find()
Fixed an inverted condition
Fixed occurences of NULL and removed internal
Fixed tests to conform to latest api
Fixup: Style violation
Fix: SEGFAULT in tests_avl_insert_multiple_destroy

The use of `malloc()` caused to allocate an avl structure with
initialized `root` pointer member. At some point when iterating through
this tree of non-existing memory, it segfauls. Allocating the avl
structure with a NULL root node causes the code to allocate _real_
nodes, which _can_ be accessed.
Fix: Possible segfaults, allocate the avl structure with NULLed memory
Remove: test_avl_alloc: We do not test the calloc() function, it has to work
Added a cast to (int*)
Removed uneeded elements array