RFR: Shenandoah options should be uintx

[Aleksey Shipilev]

shenandoah/jdk8u barfs when trying to select ShenandoahCodeRootsStyle
("improperly specified option"), because it is defined as uint, not as uintx
like other options.

Fix for 10, that will trickle down to 9 and 8u:
  http://cr.openjdk.java.net/~shade/shenandoah/options-uintx/webrev.01/

Testing: hotspot_gc_shenandoah

Thanks,
-Aleksey