File sending.
Basic ntox file sending.
Speeded up/fixed NAT hole punching and peer finding.
File sending now works on bad wireless connections.
Core now takes better care of file transfers.
nTox updated with changes in core, some file sending things fixes.
Removed useless ifdefs.
Fixed bug.
Max length of filenames is now 255 bytes.
File control packets can now be used by the person sending the file.
Merge branch 'file-transfers' of https://github.com/irungentoo/ProjectTox-Core into file-transfers
File sending added to public api.
Merge branch 'file-transfers'

File transfers are now working and in public api.
Code cleanups.
Fixed some possible bugs.
m_addfriend_norequest now prevents you from adding your own id as friend.
Fixed file sending bug.
Tox sync added.

Tox sync is a proof of concept bittorrent sync inspired application that
uses tox to sync the contents of two folders.

Currently only works on POSIX compilant operating systems.
Fixed warnings.
Code cleanups.