This moves write-barrier for writes into code to heap-write-barrier.h
and adds four new functions:
- WriteBarrierForCode(host, rinfo, object) - combined generational
  and marking write barrier.
- WriteBarrierForCode(host) - combined write barrier that rescans
  all pointers in the host (former RecordWritesIntoCode).
- GenerationalWriteBarrierForCode.
- MarkingWriteBarrierForCode.

Bug: v8:8054,v8:7490
Change-Id: Ib1e07cfa1d5998fca2fa44e2ad08c52305f1373f
Reviewed-on: https://chromium-review.googlesource.com/1174436Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55185}