Fix non-public imports to allow compilation with DMD 2.087

[don-clugston-sociomantic]

This does not address the use of deprecated features,, which still generate dozens of warnings, but it does fix the errors.

Two groups of compilation errors are fixed:

• The swarm mixins need access to the Notification type, so the imports of the Requests need to be made public.

• The NeoSupport Internal mixin has an Internals struct. The imports inside it need to be transitive.

The same changes need to be made in dmqproto and dlsproto.

[matthias-wende-sociomantic]

LGTM. Can you please add a commit that bumps the DMD version in the travis file to DMD 2.087? https://github.com/sociomantic-tsunami/dhtproto/blob/v15.x.x/.travis.yml#L43 and https://github.com/sociomantic-tsunami/dhtproto/blob/v15.x.x/.travis.yml#L45

[matthias-wende-sociomantic]

Approved. I leave it for @gavin-norman-sociomantic to merge.