RFR: 8218565: HandleMark cleanup

[Claes Redestad]

Hi,

after JDK-8218145 I noticed HandleMark::pop_and_restore became outlined
in places where it was previously inlined. Analyzing the code it seems
there are a few calls in that method that are rarely taken, so inlining
could be helped by outlining these. Doing so marginally helps static
footprint and a small reduction in instructions retired on some startup
tests on linux-x64.

When in the neighborhood I noticed some code duplication between
~HandleMark and pop_and_restore, along with a now unused debugging
counter (_nof_handlemarks - use was removed by JDK-8146850).

Webrev: http://cr.openjdk.java.net/~redestad/8218565/open.00/
Bug:    https://bugs.openjdk.java.net/browse/JDK-8218565

Testing: tier1+2, verified pop_and_restore gets inlined in more places
with a smaller footprint cost

Thanks!

/Claes