RFR 8201786: Modularize interpreter GC barriers: leftovers for ARM32

[Aleksey Shipilev]

http://cr.openjdk.java.net/~shade/8201786/webrev.01/
https://bugs.openjdk.java.net/browse/JDK-8201786

This finishes up the work for interpreter GC barriers modularization [1] for ARM32. My interest is
having a clean Epsilon GC patch, and this is the only remaining bit. The change is mostly about
moving the code around, but in some cases we have to replace the calls to "naked" stores with the
appropriate BSAsm calls too. There is a fair amount of symmetry with the x86 implementation, you may
want to cross-reference that during reviews.

Unfortunately, I have no way to test this thing thoroughly, except for running simple apps on Raspi
3 with the cross-compiled build. The largest app I tried was Wildfly Swarm demo with both Serial GC
(which covers CardTableBS) and G1 (which covers G1BS). More testing is appreciated!

Testing: arm32-hflt cross-build, some apps with Serial/G1 on Raspi 3

Thanks,
-Aleksey


[1] https://bugs.openjdk.java.net/browse/JDK-8201786