RFR: Revert part of StubGenerator to ease porting

[Aleksey Shipilev]

On 03/21/2017 11:26 AM, Roman Kennke wrote:
> This reverts our modifications to StubGenerator and related code and
> removes the 3rd stub generation phase that used to generate the
> Shenandoah stub. This makes it easier to port to platforms, because it
> would otherwise require changes in all arches.
> 
> The downside is that we cannot use our write-barrier stub in the
> interpreter. I put back in a specialized write-barrier for the
> interpreter to handle this.
> 
> I tested it on x86_64 and aarch64, Aleksey tested it on i586. Both jdk9
> and jdk8u.
> 
> http://cr.openjdk.java.net/~rkennke/fixstubgen/webrev.00/

Thank you, looks good.

*) This can be pruned:

 430   // tty->print_cr("called interpreter write barrier with: %p result: %p",
src, result);

-Aleksey