#1 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 "malloc" like in the function "medusa_sender_create" and from "pthread_create" in the function "medusa_receiver_start"?
http://medusa-audionet.svn.sourceforge.net/viewvc/medusa-audionet/src/medusa/net/sender.c?revision=97&view=markup
http://medusa-audionet.svn.sourceforge.net/viewvc/medusa-audionet/src/medusa/net/receiver.c?revision=90&view=markup