RFR: 8142362: Lots of code duplication in Copy class

[Coleen Phillimore]

Removed an unused assembly function on one platform (_Copy_conjoint_bytes), and consolidated the linux and bsd x86, and linux and bsd aarch64 copy code that was duplicated.  There's unfortunately now an #ifndef _WINDOWS in copy_x86.hpp and copy_aarch64.hpp, and I couldn't combine the duplicate copy_<arch>.S files because Windows doesn't have this file (and couldn't convince the build system to ignore the .S file for windows).
I didn't think it was worth adding an os_cpu/posix_x86 and os_cpu/posix_aarch64 directory for this small bit of code.

There could be more consolidation but the platform differences are subtle.  This change just moves around code without poking this bear.

Tested with tier1 on Oracle platforms, build on linux-x86-open,linux-s390x-open,linux-arm32-debug,linux-ppc64le-debug and Zero (zero in progress).

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Commit messages:
 - Commonify linux/bsd versions of os_cpu copy functions into cpu copy functions.
 - Removed unused Copy_ functions.

Changes: https://git.openjdk.java.net/jdk/pull/6984/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6984&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8142362
  Stats: 1627 lines in 11 files changed: 451 ins; 1162 del; 14 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6984.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6984/head:pull/6984

PR: https://git.openjdk.java.net/jdk/pull/6984