RFR: JDK-8190484 Move jvm.h, jmm.h et al to hotspot/*/include

[Magnus Ihse Bursie]

JDK-8190484 was created as a follow-up bug to the unification of the 
duplicated jvm.h, jvm_md.h and jmm.h, to determine the proper location 
of these files. This has now been decided to be hotspot/share/include 
and hotspot/os/$OS/include, respectively.

This patch moves the relevant files there, but since this also frees up 
the src/$MODULE/native/include directories for the original purpose, it 
also unifies and simplifies the build logic for these directories, so 
that common code is executed for all modules to just copy any exported 
header files from these directories, should they exist.

I'm intending to push this to jdk-hs.

Bug: https://bugs.openjdk.java.net/browse/JDK-8190484
WebRev: 
http://cr.openjdk.java.net/~ihse/JDK-8190484-move-hotspot-exported-includes/webrev.01

/Magnus