started implementation on avltrees
Working further on implementation for avltrees: insert, take, retrieve seem to be bug free but slow... . Still missing functions: destroy, take_min/man + iterating the tree
avoided object memory allocation time during inserts in avltree_test.c
finished implementation of avltree_take_min/max
changed compiler optimization and fixed syntax error in avltree.c
removed out commented code
completed destroy function and added test case for this
refactoring
Added for_each_safe-macros for lists and a corresponding test
refactoring, removing cleanup macro, adjusting rest of code, renamed macros.h to macro.h
adjusted README.md