RFR(M): 8212243: More gc interface tweaks for arraycopy and some other smaller changes in preparation for Shenandoah

[Roland Westrelin]

> I prefer the first one.

Then you have to test the type of the C2Access being dealt with. Would
you do that with virtual methods in C2Access (is_parse_access(),
is_opt_access()) or throught the _decorators maybe?

Roland.