protect against buffer overflow
only print debug messages when configured
fix wrong format string modifier
use DPRINT for logging debug messages
clear the response

Just making sure, it seems cleaner to make sure that the function
can not exit with the response in some random/undefined state
no semicolons here (empty statements)
code style consistency
check return value of rad_converse()
Merge pull request #10 from sara-nl/surfsara

SURFsara fixes and changes