#525 Ignoring network packet errors

[philipp]

Errors returned by SDLNet_UDP_Recv() are not handled correctly in "src/hardware/ipx.cpp" and "src/hardware/ipxserver.cpp".

SDLNet_UDP_Recv() is documented to return -1 on error but currently success is checked with != 0 instead of == 1.

If SDLNet_UDP_Recv() would return -1 then partially initialized packets with old data would be processed.

This is in 0.74 (and earlier) and in the trunk of the repository (r4308).