Updating nTox_win32 and adding Messenger.c method

Made changes to nTox_win32 to improve it - adding a friends listing method, and implemented the m_delfriend() method from Messenger.c

In Messenger.c I also added a method to simply return numfriends. This allows my friends list method to work but I can see it being useful for GUIs as well.

These changes have already been tested amongst severeal Windows users and are working.