RFR: [9] 2018-02-20: Bulk backports to sh/jdk9

[Aleksey Shipilev]

http://cr.openjdk.java.net/~shade/shenandoah/backports/jdk9-20180220/webrev.01/

This backports a small chunk of cleanups and bugfixes to sh/jdk9:

30b431d17fcc: [backport] ShenandoahWriteBarrierNode::find_bottom_mem() fix
8cd5e3a78fea: [backport] Move barriers into typeArrayOop.hpp direct memory accessors
80cdb1b94399: [backport] Roots verification should take the special roots first
b5a09ff17768: [backport] LotsOfCycles test timeouts
ab9dd1d11dc1: [backport] Protect C2 matchers with UseShenandoahGC

Testing: hotspot_gc_shenandoah {fastdebug|release}

Thanks,
-Aleksey