RFR: 8287512: continuationEntry.hpp has incomplete definitions

[Ron Pressler]

Please review this small change, which cleans up continuationEntry.hpp and fixes incomplete definitions.

Passes tier1

-------------

Commit messages:
 - Clean up continuationEntry.hpp

Changes: https://git.openjdk.java.net/jdk/pull/8944/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8944&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8287512
  Stats: 19 lines in 3 files changed: 7 ins; 7 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8944.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8944/head:pull/8944

PR: https://git.openjdk.java.net/jdk/pull/8944