[13] RFR (S): 8217918: C2: -XX:+AggressiveUnboxing is broken

[Vladimir Ivanov]

https://bugs.openjdk.java.net/browse/JDK-8217918
http://cr.openjdk.java.net/~vlivanov/8217918/webrev.00/

When -XX:+AggressiveUnboxing is enabled, LoadNode::split_through_phi() 
produces Phi nodes with non-negative _inst_mem_id & _inst_id early 
enough, so it breaks PhaseRenumber pass which doesn't support nodes with 
embedded IDs.

Proposed fix tracks nodes with embedded IDs and updates them once 
renumbering pass over the graph is over.

Testing: hs-precheckin-comp, tier1-5

Best regards,
Vladimir Ivanov