Simple data structures practice.

• c version, list(two implementions), stack and binary tree only.

• java version, list, stack and binary tree only.

• objective c version, list only.

• cpp version, list only.

Becuase these two language specific implemention is done in same period, so variable and functions names are mostly consistent.

• Add hashtable.

• Add general tree.

• Add ant build for java version.