binary metadata

[Tom Tromey]

Bryce> Having the compiler use it is an interesting idea, however -
Bryce> the metadata is complete enough, so really its just down to some
Bryce> design/technical challenges in having the compiler read from the
Bryce> object files.

The compiled code doesn't have the deprecated tag, and perhaps won't
have @Retention(CLASS) annotations either.  (The new @Deprecated
annotation seems to have @Retention(RUNTIME), which looks weird, but
would let this work.)  That's a barrier to directly using the .so in
the compiler.

FWIW, I looked into this a bit for gcjx.  It looks easy in that
context, if the annotation problems are solved.  We could of course
just declare that @Retention(CLASS) annotations are to be kept in the
.so, perhaps optionally so the space-challenged can avoid bloat.

It is tempting to think that we could avoid making .class files at
all, but I suspect we'd still want them around for things like
Eclipse.

Tom