Add implementation of stack in OCaml.
Add implementation of stack in OCaml.

ZoranPandovski/al-go-rithms,ZoranPandovski/al-go-rithms,ZoranPandovski/al-go-rithms,ZoranPandovski/al-go-rithms,ZoranPandovski/al-go-rithms,ZoranPandovski/al-go-rithms,ZoranPandovski/al-go-rithms,ZoranPandovski/al-go-rithms,ZoranPandovski/al-go-rithms,ZoranPandovski/al-go-rithms,ZoranPandovski/al-go-rithms,ZoranPandovski/al-go-rithms,ZoranPandovski/al-go-rithms,ZoranPandovski/al-go-rithms,ZoranPandovski/al-go-rithms,ZoranPandovski/al-go-rithms,ZoranPandovski/al-go-rithms,ZoranPandovski/al-go-rithms,ZoranPandovski/al-go-rithms,ZoranPandovski/al-go-rithms