[dmd-beta] Regression fixes for DMD 2.066 need review and pulling

[Walter Bright via dmd-beta]

There has been a lot of valid criticism about us releasing 2.066 with 
outstanding regressions.

https://issues.dlang.org/buglist.cgi?bug_severity=regression&bug_status=NEW&bug_status=ASSIGNED&bug_status=REOPENED&list_id=88763&query_format=advanced

Fixes exist:

https://github.com/D-Programming-Language/dmd/pull/3884
https://github.com/D-Programming-Language/dmd/pull/3896
https://github.com/D-Programming-Language/dmd/pull/3879
https://github.com/D-Programming-Language/dmd/pull/3889
https://github.com/D-Programming-Language/dmd/pull/3897

Let's get them reviewed/pulled and do a 2.066 point release.