Added a linked list implementation.
Added ERROR() and WARNING() for debugging.
Merge pull request #362 from KostyaKow/master

Added linked list and stuff for debugging.
Merge branch 'master' of https://github.com/irungentoo/ProjectTox-Core
code format/clean up
Merge pull request #363 from JFreegman/master

code format/clean up
Merge remote-tracking branch 'upstream/master'