Imported Upstream version 3.1.1.26+dfsg2
Merge tag 'upstream/3.1.1.26+dfsg2'

Upstream version 3.1.1.26+dfsg2
Compile missing pieces of bootstrap
Add bootstrap-required binaries to fsharp binary package
Ensure 4.3.0 assembly gets installed (Closes: #767265)
Finalize changelog