#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" and "calloc" like in the function "cmd_loop" and from "fclose" in the function "ftp_retr"?
http://stftp.cvs.sourceforge.net/stftp/stftp/cmdloop.c?revision=1.17&view=markup
http://stftp.cvs.sourceforge.net/stftp/stftp/ftp.c?revision=1.11&view=markup