RFR: Fix build failures due to undeclared ShenandoahOldHeuristics

[Aleksey Shipilev]

Some configs, notably Zero, does not build due to:


* For target hotspot_variant-zero_libjvm_objs_shenandoahAdaptiveHeuristics.o:
In file included from /home/buildbot/worker/build-shenandoah-jdkX-linux/build/src/hotspot/share/gc/shenandoah/heuristics/shenandoahAdaptiveHeuristics.hpp:28:0,
                 from /home/buildbot/worker/build-shenandoah-jdkX-linux/build/src/hotspot/share/gc/shenandoah/heuristics/shenandoahAdaptiveHeuristics.cpp:27:

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Commit messages:
 - Fix build failures due to undeclared ShenandoahOldHeuristics

Changes: https://git.openjdk.java.net/shenandoah/pull/34/files
 Webrev: https://webrevs.openjdk.java.net/?repo=shenandoah&pr=34&range=00
  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/shenandoah/pull/34.diff
  Fetch: git fetch https://git.openjdk.java.net/shenandoah pull/34/head:pull/34

PR: https://git.openjdk.java.net/shenandoah/pull/34