[master] RFR: Preserve Klass* in leak profiler

[Roman Kennke]

The JFR leak profiler uses the mark word for marking objects during traversal, and for storing pointers to Edges. We need to preserve the compressed Klass* in the upper part of the mark-word during the traversal.

The change is based on: ttps://github.com/openjdk/jdk/pull/5918

Testing:
 - [x] jdk/jfr (x86_64)
 - [x] jdk/jfr (x86_32)
 - [x] tier1
 - [ ] tier2

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Commit messages:
 - Merge branch 'master' into fix-jfr-2
 - Merge branch 'pull/5918' into fix-jfr-2
 - remove -1
 - constants
 - Fix 32bit build
 - Merge branch 'master' into fix-jfr-2
 - In leakprofiler, don't override Klass when marking objects
 - Merge branch 'pull/5918' into fix-jfr-2
 - spelling
 - prepare leakprofiler for lilliput

Changes: https://git.openjdk.java.net/lilliput/pull/21/files
 Webrev: https://webrevs.openjdk.java.net/?repo=lilliput&pr=21&range=00
  Stats: 113 lines in 4 files changed: 81 ins; 23 del; 9 mod
  Patch: https://git.openjdk.java.net/lilliput/pull/21.diff
  Fetch: git fetch https://git.openjdk.java.net/lilliput pull/21/head:pull/21

PR: https://git.openjdk.java.net/lilliput/pull/21