Heads-up: multiple crashes on AArch64

[Aleksey Shipilev]

http://cr.openjdk.java.net/~shade/shenandoah/crashes/aarch64/

hs_errs above, the command lines are there too. This seems to only happen with Shenandoah, and only
on aarch64.

It looks like there are two issues:
  a) Some instruction gets too large with C1. This happens on all versions: sh/jdk, sh/jdk11,
sh/jdk10, sh/jdk8.
  b) Some locking code is broken with C2. This happens with sh/jdk, but not anywhere else.

Roman, can you take a look, please?

Thanks,
-Aleksey