RFR: 8199696: Remove Runtime1::arraycopy

[Erik Österlund]

Hi,

The Runtime1::arraycopy stub appears to only be used on S390 because 
there is no StubRoutines::generic_arraycopy() provided. However, C1 
could then simply take a slow path and call its arraycopy stub that 
performs a native call. Then this logic may be removed.

I added an assert on each platform that I think should have a 
generic_arraycopy() stub, and added a branch to the slow path on S390 if 
there is no such stub. If a stub is eventually added on S390, it should 
automatically pick that up.

Webrev:
http://cr.openjdk.java.net/~eosterlund/8199696/webrev.00/

Bug ID:
https://bugs.openjdk.java.net/browse/JDK-8199696

Thanks,
/Erik