RFR: All definitions should start with Shenandoah*

[Aleksey Shipilev]

Hi,

Lacking namespaces isolation, we need to make sure all our definitions start with appropriate
Shenandoah* prefix. This avoids clashes with anything else in Hotspot during the VM linkage, and
makes accidental dependencies harder to make.

Webrev:
  http://cr.openjdk.java.net/~shade/shenandoah/rename-shenandoah-prefix/webrev.01/

Going to backport this to 9 and 8u later to help there too.

Testing: hotspot_gc_shenandoah

Thanks,
-Aleksey