RFR: Split out ContinuationEntry and ContinuationWrapper classes [v3]

[Coleen Phillimore]

> Moved ContinuationEntry and ContinuationWrapper to their own files.
> There's a bit of inconsistency because 3 ContinuationEntry functions are in ContinuationHelper_cpu.inline.hpp - maybe we should have continuationEntry_cpu.inline.hpp files for just the three.
> I'd like to change the name ContinuationEntry to ContinuationAnchor or ContinuationFrameAnchor but want to study how that would look a bit more first.
> Tested with other platforms and testing with loom-tier1 as sanity.

Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:

  Stefan's cleanups

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

Changes:
  - all: https://git.openjdk.java.net/loom/pull/145/files
  - new: https://git.openjdk.java.net/loom/pull/145/files/86423721..6cdabe23

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=loom&pr=145&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=loom&pr=145&range=01-02

  Stats: 18 lines in 6 files changed: 3 ins; 2 del; 13 mod
  Patch: https://git.openjdk.java.net/loom/pull/145.diff
  Fetch: git fetch https://git.openjdk.java.net/loom pull/145/head:pull/145

PR: https://git.openjdk.java.net/loom/pull/145