Merge master to dev16.1#6252

Merged

brettfo merged 7 commits intodev16.1from

merges/master-to-dev16.1

Feb 19, 2019

Commits on Feb 7, 2019

fix package signing (#6207) (#6208)
brettfo
authored

Commits on Feb 8, 2019

We don't ever set the value FCS_RETAIN_BACKGROUND_PARSE_RESULTS (#6212)
KevinRansom
authored
Ensure core tests pick up fsharp.core nuget packages from artifacts build (#6206)
KevinRansom
authored

Commits on Feb 13, 2019

Update mono props: support OSX and more .NET Framework versions (#6181)

baronfel
authored and
KevinRansom
committed

Commits on Feb 17, 2019

fix double-build of vsix packages (#6233)

brettfo
authored and
KevinRansom
committed

Commits on Feb 19, 2019