#6 Check return codes everywhere

[Markus Elfring]

Some checks for return codes are missing.

Examples:
Would you like to add more error handling for return values from "fprintf" like in the function "help" and from "fclose" in the function "route_listadd"?
http://rtnet.svn.sourceforge.net/viewvc/rtnet/trunk/rtnet/tools/rtroute.c?revision=1075&view=markup