[Releasing] 5.5.1 ChangeLog contains important information, please make sure it's in the announcement

[Thiago Macieira]

For 5.5.0, the announcements did not include any link to the changelog, which 
included important information to users. I fixed that post-release.

Let's please not make the same mistake for 5.5.1.

Also, please don't link to individual modules' changelogs. People won't read 
that. I prepared a master changelog, which you can find at

https://codereview.qt-project.org/#/c/126113/1/dist/changes-5.5.1-master

This file will not be in the release, so someone please copy & paste the text 
into a page somewhere that is linked from the release announcement.
-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel Open Source Technology Center