Request for reviews (L): 7125896: Eliminate nested locks

[Vladimir Kozlov]

http://cr.openjdk.java.net/~kvn/7125896/webrev

7125896: Eliminate nested locks

Nested locks elimination done before lock nodes expansion by looking for outer 
locks of the same object. Commoning (GVN) of BoxLock nodes is switched off 
because nested locks elimination requires separate BoxLock node for each locked 
region to generated correct debug info for deoptimization. As result there could 
be merges (and Phi nodes) of BoxLock nodes. One such merge generated by 
ciTypeFlow (cloning loop head) is avoided but there could be other cases so new 
code is added to handle it.

New code is under new product flag EliminateNestedLocks.

Also added missed KILL effect for box register in fastlock and fastunlock mach 
nodes definitions.

Tested with full CTW, nsk, jtreg tests, refworkload.

Thanks,
Vladimir