RFR(M) JDK-8031819: Remove legacy jdk checks and code

[Daniel D. Daugherty]

On 6/5/14 11:26 PM, David Holmes wrote:

 > But everyone needs to be very aware that once this goes in you
 > can forget about placing a JDK 9 VM anywhere but a JDK 9 JDK.
 > (Or did we already hit that?)

This caught my eye... Have we already reached a point where we
can't put the current JDK9 JVM into various JDK8 builds? I know
we have restrictions about putting the current JVM (and the
HSX-25 JVM) into JDK7...

If the current JDK9 JVM (prior to this changeset) can still be
dropped into JDK8 and this changeset makes it so that the JDK9
JVM can no longer be dropped into JDK8, then we need to get
wider feedback than hotspot-runtime-dev at ...

In particular, the HotSpot Compiler and Performance teams should
be notified since dropping the current JVM into an older JDK is
one of their standard failure analysis techniques; don't know
if the HotSpot GC team does that trick much.

Dan