awk: remove temporary files

[mknos]

• awk wrapper doesn't clean up after itself and I am left with all these spam files... a2pin.6695 a2pout.6695 a2pin.6697 a2pout.6697 a2pin.6699 a2pout.6699 a2pin.6702 a2pout.6702 a2pin.6951 a2pout.6951 a2pin.6953 a2pout.6953
• unlink before exit is better, whether or not the files are written in /tmp