RFR: JDK-8189430: make/hotspot/copy/Copy-java.base.gmk in wrong location after consolidation

[Erik Joelsson]

In the consolidation restructuring, I missed merging the contents of 
make/hotspot/copy/Copy-java.base.gmk with make/copy/Copy-java.base.gmk. 
The only relevant part that needs to be preserved is the optional 
copying of libffi.so.? which we need when building zero internally at 
Oracle. The rest of the contents of this file is just copy rules for 
header files that are currently disabled. These header files are 
currently being copied from the old jdk repository instead of the old 
hotspot repository. Keeping these unused rules around serves no point.

This patch moves the libffi copying to the correct place and discards 
the rest of the forgotten file.

Webrev: http://cr.openjdk.java.net/~erikj/8189430/webrev.01/

Bug: https://bugs.openjdk.java.net/browse/JDK-8189430

/Erik