Passed: OpenSmalltalk/opensmalltalk-vm#1862 (201911282316 - 4710c5a)

CogVM source as per VMMaker.oscog-eem.2598

Spur: VMMaker.oscog-cb.2595

Fixed a fascinating bug in Planning compactor.

Sometimes Planning decides to go for a multi-pass compaction, but in one
compaction it compacts it all, so that firstFreeObject is the last object on
heap, on the object after firstFreeObject is outside of the heap. Planning gets
confused in this case, while everything is compacted. So I changed to abort
compaction in that case, since everything is already compacted.

Avoid inlining endCompaction to prevent duplication in compact.

Make a minor refactoring to reinitializeScanFrom: to make it more readable
(move assignment to firstMobileObject into
scanForFirstFreeAndFirstMobileObjectFrom:).

Improve the ImageLeakChecker to bounds check objects while swizzling, and hence
detect the damaged images produced by the issue 444 planning compactor bug as
corrupted.

Refactor swizzleObj: to swizzleObj:in: so that ImageLeakChecker/
SpurLeakCheckingSegmentManager can produce more informative diagnostics.

Improve the leak checker to first bounds check oops against the heap extent
before probing the heap map. This prevents ImageLeakChecker from crashing
on issue 444 corrupted images.