Java: add Class protection domain field

[Bryce McKinlay]

In order to fully implement the Java 2 ClassLoader security semantics
and API, we need a new field in java.lang.Class in which to track the
security environment (ProtectionDomain) that an individual class is
assigned to (arguably, any attempt to enforce security for a native
class is a waste of time, but libjava can, of course, load bytecode
from arbritrary sources, so we do want a security framework
implementation).

As the layout of java.lang.Class is dictated by the compiler, a
compiler patch is required to add this new field.

I'll post the runtime part of this patch soon, but wanted to get this
rubber-stamped first. OK?

regards

  [ bryce ]