Release D 2.078.0

[Nathan S.]

DMD64 2.078.0 on Linux and macOS is taking wildly longer to build 
and run unittests for mir-algorithm. The extra time appears to be 
related to release mode optimizations.

Build logs:
https://travis-ci.org/libmir/mir-algorithm/builds/324052159

DMD 2.077.1 for linux32: 3 min 20 sec
DMD 2.077.1 for linux64: 3 min 16 sec
DMD 2.077.1 for mac64: 5 min 4 sec

DMD 2.078.0-rc.1 for linux32: 13 min 30 sec
DMD 2.078.0-rc.1 for linux64: 9 min 39 sec
DMD 2.078.0-rc.1 for mac64: 10 min 56 sec, then the job was 
aborted

The above tests all include a non-release build and a release 
build. On my mac laptop running DMD 2.078.0, building and running 
the mir-algorithm unittests takes 8 seconds normally but takes ~3 
minutes 49 seconds with dub options "releaseMode", "optimize", 
"inline", "noBoundsCheck".

I don't see any new compiler optimizations in the changelog. Any 
idea of what could be causing this?