Update binding to the latest toxcore version

Function tox.new() now accepts an optional table with options;
Remove method Tox.setSendsReceipts(), as done in the core.
Makefile: link to rt (for mutexes) and pulls C standard back to C99

Older GCCs do not accetp -std=c11;
Add an echo bot for example
Remove lua_tox_set_sends_receipts from the headers too
Update API to the last toxcore version

Functions send_message_withid and send_action_with were removed.
Merge pull request #1 from ittner/update-new-version

Update API to work with the latest toxcore version