RFR: 8156032: Clean up parallel GC specific code from vm/gc/shared/preservedMarks.cpp

[Leonid Mesnik]

Hi

Could you please review following patch which remove PS specific code 
from vm/gc/shared.
Webrev: http://cr.openjdk.java.net/~lmesnik/8156032/webrev.00/ 
<http://cr.openjdk.java.net/%7Elmesnik/8156032/webrev.00/>
Bug: https://bugs.openjdk.java.net/browse/JDK-8156032

Fix is tested with JPRT.

Leonid