RFR: 8232648: ZGC: Move ATTRIBUTE_ALIGNED to the front of declarations

[Stefan Karlsson]

Hi all,

Please review this patch to move ATTRIBUTE_ALIGNED to the front of 
declarations.

https://cr.openjdk.java.net/~stefank/8232648/webrev.01/
https://bugs.openjdk.java.net/browse/JDK-8232648

This is done because the Windows compiler requires ATTRIBUTE_ALIGNED to 
be put at the front of declarations. A new macro (ZCACHE_ALIGNED) is 
introduced, and used, to shorten the affected lines.

Thanks,
StefanK