JDK 16 RFR of JDK-8235496 : "Start of release updates for JDK 16" and related work

[Joe Darcy]

Hello,

The start of JDK 16 is right around the corner with JDK 15 forking off 
from jdk/jdk at ramp down 1 [1].

Please review the usual build-related portions of

     http://cr.openjdk.java.net/~darcy/8235496.4/

The build updates were as expected; the symbol information for JDK 15 
was extracted from JDK 15 b24. This may be updated to a later build for 
initial inclusion in JDK 16.

Related review threads started on compiler-dev and hotspot dev.

Thanks,

-Joe

[1] http://openjdk.java.net/projects/jdk/15/