Bump meteor core package version to 1.8.4.
Bump meteor core package version to 1.8.4.

This version of `meteor` has no other changes from 1.8.3, though it has
been intentionally published with version 1.6.0.1 of the Meteor tool,
rather than Meteor 1.6.1.

This is to accommodate for the change made in
https://github.com/meteor/meteor/commit/57533d22 which changed the way
code is packaged by the Isobuild linker.  Since packages which use a compiler
plugin include the linked content of the plugin within their published
package source, the linked source of a compiler plugin's
host package, which was published with Meteor 1.6.1, contains this new usage of
`Package._define`.  Unfortunately, the `meteor` packages pre-1.8.2
doesn't have the runtime definition of `Package._define`, and therefore fails,
as seen in https://github.com/meteor/meteor/issues/9700.

Some older versions of Meteor don't pin core packages quite in the right
way (1.4.2.x was notorious for this, though we believe it to be fixed in
Meteor 1.5.2+ thanks to https://github.com/meteor/meteor/commit/cfdc69bf71),
so this will be a bit problematic until those versions are no longer
actively used.  This is similar to the problem older versions of Meteor
would have consuming code which was packaged with newer versions of
Meteor and might contain newer ECMAScript syntax which doesn't need
transpilation on newer Node.js versions, but did on the Node.js runtime
included in older versions of Meteor.

Fixes: https://github.com/meteor/meteor/issues/9700.

Hansoft/meteor,Hansoft/meteor,Hansoft/meteor,Hansoft/meteor,Hansoft/meteor,Hansoft/meteor,Hansoft/meteor