RFR [10]: 8180423: Remove flag UseRelocIndex

[Claes Redestad]

Hi,

the develop flag UseRelocIndex has been both disabled and broken
for quite some time and I think it should be removed (if the now
dead optimization is worthwhile it needs to be re-designed anyhow).

Bug: https://bugs.openjdk.java.net/browse/JDK-8180423
Webrev: http://cr.openjdk.java.net/~redestad/8180423/hotspot.00/

While some of this does show up in startup profiles, e.g.,
RelocIterator::create_index is called 242 times in one test,
the cost is definitely infinitesimal and this should be seen
primarily as cleaning out dead, broken and untested code.

Testing: RBT hs-tier2,hs-tier3-comp

Thanks!

/Claes