#4 Security fixes for denial of service attacks

[Manuel Moos]

This fixes the recently discovered security problems.

0.2.8.X and 0.3.0 are affected by:
- A forged client can request too many network object
ID numbers from the client, freezing it
- A clumsy remote administrator can issue commands
that produce too much output, freezing the server

All versions are affected by:
- A forged client can send network objects with wrong
owner information, crashing/terminating the server

The patch for 0.2.6 is yet untested, the current
client can't connect to a 0.2.6 server on the LAN.

[Manuel Moos]

Patch for 0.2.6.X and 0.2.7.0

[Manuel Moos]

Logged In: YES
user_id=34808

Patch for 0.2.7.1

[Manuel Moos]

Patch for 0.2.8.X and 0.3.0

[Manuel Moos]

Logged In: YES
user_id=34808

The 0.2.6 patch was tested with an modified 0.2.6 client as
the attacker and worked fine.

[Manuel Moos]

Patch for 0.2.7.1