#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 "fprintf" like in the function "write_one_request" and from "fclose" in the function "append_data"?
http://manhattan.svn.sourceforge.net/viewvc/manhattan/trunk/src/admin_add_courses.c?revision=253&view=markup