RFR(S): 8017313: PPC64 (part 6): cppInterpreter: stack handling improvements

[Lindenmaier, Goetz]

Hi,

We precompute the stack limit for overflow checks and save this
limit in the thread.  This simplifies the assembler coding checking
the stack overflow. This change contains the necessary shared
functionality. It can easily be ported to other platforms, too.
http://cr.openjdk.java.net/~goetz/webrevs/8017313-stack/

Please review this change.

Best regards,
  Goetz.

PS: I removed some parts of patch 0006 because I found a better
platform-only solution.