CogVM source as per VMMaker.oscog-eem.3488

Fix bad bug with scavenging ephemerons. The old code scavenged only the first
slot of a scavenged ephemeron, instead of the correct behaviour which is to
scavenge everything but the first slot of the scavenged ephemeron.

To this end:
  Refactor scavengeReferentsOf: into separate routines fror pointer objects,
  indexable pointer objects (including contexts), weak objects, ephemerons,
  and compiled methods.
  Make all SpurMemoryManager format code accessors macros.
  In copyAndForward:
	Rewrite shouldBeTenured: to be inlinable in an if, and evaluate it only if futureSpace woud not overflow. This is an or so does less work.
	Streamline the testing for weak & ephemeron objects.

Now that ephemerons are being used in anger lose a spurious assert in
updatePointersInSurvivingObjects.

src/spur32.cog.lowcode/cointerp.h

@@ -1,5 +1,5 @@
 /* Automatically generated by
-	CCodeGeneratorGlobalStructure VMMaker.oscog-eem.3487 uuid: 0cb5e53f-fb06-4acf-87f3-c6ec09b46e4b
+	CCodeGeneratorGlobalStructure VMMaker.oscog-eem.3488 uuid: 077ba5f9-f78e-4a31-b0e4-9270558f594b
 	(Compiler-eem.512)
  */
 
@@ -197,7 +197,6 @@ extern sqInt maxSlotsForNewSpaceAlloc(void);
 extern sqInt maybeMethodClassOfseemsToBeInstantiating(sqInt methodObj, sqInt format);
 extern sqInt minSlotsForShortening(void);
 extern sqInt nilObject(void);
-extern sqInt nonIndexablePointerFormat(void);
 extern sqInt numBytesOf(sqInt objOop);
 extern usqInt numSlotsOf(sqInt objOop);
 extern sqInt objectAfter(sqInt objOop);
@@ -307,6 +306,7 @@ extern sqInt suppressHeartbeatFlag;
 #define identityHashHalfWordMask() 0x3FFFFF
 #define indexablePointersFormat() 3
 #define isForwardedObjectClassIndexPun() 8
+#define nonIndexablePointerFormat() 1
 #define numSlotsFullShift() 56
 #define numSlotsHalfShift() 24
 #define numSlotsMask() 0xFF