hg: build-infra/jdk9/hotspot: Improve support for zero.

[magnus.ihse.bursie at oracle.com]

Changeset: 1410e24cdb2a
Author:    ihse
Date:      2015-10-08 12:30 +0200
URL:       http://hg.openjdk.java.net/build-infra/jdk9/hotspot/rev/1410e24cdb2a

Improve support for zero.

! makefiles/Common.gmk
! makefiles/CompileJvm.gmk
! makefiles/GenerateSources.gmk
! makefiles/JvmFeaturesConf.gmk
! makefiles/JvmPlatforms.gmk
! makefiles/JvmPlatformsConf.gmk