RFR: Cleanup ASM leftovers

[Roman Kennke]

This patch removes the jmpb_if_possible() and jccb_if_possible() crap
that we have in our ASM code, and reverts the relevant parts to upstream
code. This is a leftover from when we tried to make barriers in locking
code finer-grained. We now do WB wholesale before even going into that
code, and don't need this stuff anymore.

Passes: tier3_gc_shenandoah

http://cr.openjdk.java.net/~rkennke/asmcleanup/webrev.00/

Ok?