Update to aarch64-shenandoah-jdk8u212-b04-shenandoah-merge-2019-04-30.
    
    Update version logic to handle -shenandoah* tag suffix.
    Drop PR3634 as applied upstream.
    Adjust 8214206 fix for S390 as BinaryMagnitudeSeq moved to shenandoahNumberSeq.cpp
    Update 8214206 to use log2_long rather than casting to intptr_t, which may be smaller than size_t.