Minor comment changes in server-connection-manager.h
Addressed some warnings due to non-matching data types.
Added virtual destructor to Holder. This is horrible, planning to change
the whole class in the near future.
Addressed a few other warnings:
- don't return false when you really meant to return NULL (bad!).
- use unsigned short int when the int is well, unsigned and short.
- a few casts that seemed relatively safe.
Addressed warnings in tun-tap.* files.