wumpus: Fix use after free leading to possible memory corruption when the wumpus eats a player

CID: 1170468
os_trace: Fix inverted NULL check in trace_kill_exec()

CID: 1170539
gen_echoserver: Fix use after free in my_rhandler()

CID: 1170467
gen_echoserver: Fix inadequate check of the return value of recv()
gen_listenerdemo: Fix uninitialized memory being passed to do_packet() from my_rhandler()

CID: 1170502
gen_listenerdemo: Fix inadequate check of the return value of recv()
dnsbl: Fix memory leak in dnsbl_config_handler()

CID: 1170515
Merge pull request #29 from attilamolnar/master+fixes

Fixes for bugs discovered by Coverity Scan and myself