fix comments of some files
Don't assume that all callbacks are set.

If one of callbacks is not set, the application crashes.
This is the case when you update the library and the update adds more
callbacks, or when you simply don't want to receive some of the updates
(callbacks).
In any case, defining all callbacks shouldn't be mandatory.
Merge pull request #60 from nurupo/master

Don't assume that all callbacks are set.
Merge branch 'master' of https://github.com/sometwo/ProjectTox-Core into sometwo-master

Conflicts:
	core/Messenger.c
Fixed comments in other files as per request of jvrv
More changes made to comments, as requested by jvrv
Merge pull request #62 from Captainhat/master

More comments in core fixed
Fixed header inclusion for Windows
Merge pull request #63 from nurupo/master

Fixed header inclusion for Windows
Make nTox resolve DNS addresses.
Fix sign on function
Merge pull request #65 from stal888/addr-resolve

Add DNS resolving to nTox
Cleaned up some clarity issues

Probably better to host the logo on tox.im than rbt.asia
Merge pull request #66 from m3hr/master

Cleaned up some clarity issues
Added address resolving function (Thank you stal).
Merge pull request #67 from nurupo/master

Added address resolving function (Thank you stal).
Updated nTox
Merge pull request #68 from nurupo/master

Updated nTox
Fixed segfault.
Don't exit on arrow keys