4 new package feeds: pthsem, libesmtp, knxd, linknx

I would like to add feeds for 4 new packages and become maintainer for them:
pthsem: should replace the feed in old packages
libesmtp: new feed in libs
knxd: new feed in net
linknx: new feed in net
I hope I have fulfilled the guidelines for contribution. This is my first commit on github

signed-off-by: Othmar Truniger <github@truniger.ch>