[VM] Don't try to disassemble Stop pseudoinstruction
[VM] Don't try to disassemble Stop pseudoinstruction

R=9f8b31e960a68dade71618f1ff6da6e23a1edfc9@google.com

This was causing crashes on OSs that place constant strings at high
addresses.
Bug:
Change-Id: Id61c6c7e817a7bb44fdc998f5b918e61b971153a
Reviewed-on: https://dart-review.googlesource.com/18546
Reviewed-by: Zach Anderson <9f8b31e960a68dade71618f1ff6da6e23a1edfc9@google.com>
Commit-Queue: Zach Anderson <9f8b31e960a68dade71618f1ff6da6e23a1edfc9@google.com>

dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk