RFR: JDK-8129961 : SIGSEGV when copying to survivor space

[Eric Caspole]

Hi everybody,
Please review this fix for JDK-8129961

  https://bugs.openjdk.java.net/browse/JDK-8129961

  http://cr.openjdk.java.net/~ecaspole/JDK-8129961/webrev/

The problem was that the enum GenCollectedHeap::YoungGen == 0  and it 
was interpreted as "false" in no_allocs_since_save_marks() after a 
recent refactoring.

Since there is no place in the code either serial gc or parNew where it 
ever passes "false" to avoid rescanning young gens, I want to remove the 
parameter so it will always scan young and old gens. That is simpler to 
read and removes this type of problem.
Passed JPRT.
Let me know what you think.
Thanks,
Eric