RFR: Use constant template arg to build matrix/no-matrix version of partial GC process_oop()

[Roman Kennke]

as $SUBJECT says. should save a few cycles to decide whether or not we
need to update the matrix (which we know at compile-time).

BTW: C++11 has a nice feature. With C++11 we could declare bool
update_matrix as constexpr, which, as far as I understand it, would do
the same as a template arg. (And save us this whole currying mess that
we have in conc mark...)

http://cr.openjdk.java.net/~rkennke/templ_proc_oop/webrev.00/
<http://cr.openjdk.java.net/%7Erkennke/templ_proc_oop/webrev.00/>

Roman