RFR(XXS): 8235931: add OM_CACHE_LINE_SIZE and use smaller size on SPARCv9 and X64

[Daniel D. Daugherty]

Greetings,

I'm extracting another standalone fix from the Async Monitor Deflation
project (JDK-8153224) and sending it out for review (and testing)
separately. This is an XXS sized fix, but since it involves cache
line sizes I don't think a trivial review is appropriate.

     JDK-8235931 add OM_CACHE_LINE_SIZE and use smaller size on SPARCv9 
and X64
     https://bugs.openjdk.java.net/browse/JDK-8235931

Here's the webrev URL:

     http://cr.openjdk.java.net/~dcubed/8235931-webrev/0-for-jdk15/

Folks that have reviewed JDK-8153224 will recognize these changes as
a subset of the cache line changes from the Async Monitor Deflation
project. It's a subset because there are more fields that need to be
on separate cache lines in the Async Monitor Deflation project.

These changes are being tested in a Mach5 Tier[1-3] run that's still
running (JDK14 ATR has priority). I've also run these changes thru
a set of 10 SPECjbb2015 runs; I'm waiting for my various SPECjbb2015
runs to finish so I can do the analysis.

Thanks, in advance, for comments, questions or suggestions.

Dan