RFR: JDK-8154343: Make SATB related code available to other GCs

[Kim Barrett]

> On Jul 28, 2018, at 7:13 AM, Roman Kennke <rkennke at redhat.com> wrote:
> 
> Am 28.07.2018 um 01:17 schrieb Kim Barrett:
>> 
>> I have in mind something that I think will be simpler than that, but need
>> to spend some time working through the details.  I’ll let you know what
>> I come up with.
> 
> Ok, I'll wait for you then :-)
> 
> Cheers,
> Roman

[I'm finishing up the remaining work for Roman, now that the
preliminary refactoring and cleanup changes are complete.]

Please review this move of PtrQueue.[ch]pp and satbMarkQueue.[ch]pp
files from the gc/g1 directory to gc/shared.

The change consists of (1) moving the files, (2) updating the include
guards in the moved headers, and (3) updating #includes to account for
the move.

CR:
https://bugs.openjdk.java.net/browse/JDK-8154343

Webrev:
http://cr.openjdk.java.net/~kbarrett/8154343/open.00/

Testing:
Mach5 tier1.