Tweak ANNONCE

Fix build

Read the source file timestamp *before* preprocessing (#6106)

MERGED from commit d82da29

Update ANNOUNCE for 7.4.1

Set configure.ac to build the 7.2.2 release

Expand on the unicode changes in the release notes

Introducing a datatype for WorkLists that properly prioritizes equali…

…ties.

We were not prioritizing the interaction of equalities in the worklist, because
pre-canonicalization solved the constraints one by one, in their arrival order.
This patch fixes this, so it's a generally useful improvement, mainly for
efficiency. It makes #4981 go away, although it's not a definite answer to the
cause of the problem. See discussion on Trac.