RFR: Expand LRB after compare-and-swap in C2 not in assembler

[Roman Kennke]

This removes one TODO-item from the LRB patch and moves the LRB from
assembler into C2 ideal graph. It should also fix one failure we've seen
in CI, which complained about missing LRB after CAE.

http://cr.openjdk.java.net/~rkennke/lrb-cae/webrev.00/

Testing: hotspot_gc_shenandoah, specjvm-compiler

Ok?

Roman