add download links to rpm and deb; fix a few others

 - add download links for the .rpm and .deb for 2.9.2, 2.9.3, 2.10.2,
   2.11.0-(M2, M3, M4),
 - add missing source links for 2.9.2 and 2.9.3,
 - fix brocken source link for 2.10.1.

This fixes #113.