[8u] RFR for backport of 8154156: PPC64: improve array copy stubs by using vector instructions

[Kazunori Ogata]

Hi,

May I get review for enhancement backport of 8154156: PPC64: improve array 
copy stubs by using vector instructions?

To make this patch buildable (and usable by other planned backports listed 
in [1]), I cherry picked config_dscr() and its dependent code from [2,3] 
and has_mfdscr() from [4].

Original patch: http://hg.openjdk.java.net/jdk/jdk/rev/c9d756fa846e
Weberv: http://cr.openjdk.java.net/~horii/jdk8u_aes_be/8154156/webrev.01/

I confirmed it was buildable for both relase and fastdebug builds, and 
JTREG caused no degradation.


Refs:
[1] 
http://mail.openjdk.java.net/pipermail/ppc-aix-port-dev/2018-December/003818.html
[2] 8149655: PPC64: Implement CompactString intrinsics
    http://hg.openjdk.java.net/jdk/jdk/rev/6241574f5982
[3] 8080684: PPC64: Fix little-endian build after "8077838: Recent 
developments for ppc"
    http://hg.openjdk.java.net/jdk/jdk/rev/12ccf8b26eb0 
[4] 8077838: Recent developments for ppc.
    http://hg.openjdk.java.net/jdk/jdk/rev/c703c89fddbf


Regards,
Ogata