[11u] RFR(S): 8241234: Unify monitor enter/exit runtime entries.

[Lindenmaier, Goetz]

Hi Andrew, 

> > I'm not really happy with 11 staying behind 11-oracle in the JVMCI issue. 
> What JVMCI issue is this? Please explain. All that I see is a faster
> "slow" locking path for monitors.

This was meant as a more general comment. I wanted to 
address that we don't integrate many of the JVMCI changes
so the OpenJDK 11 is probably not usable with graal.
The comment was not tailored to this specific change.
Unfortunately our team has not the capacity to look at 
JVMCI/graal.  

Best regards,
  Goetz.