Extensive changes to utilize compiled code debugging information:

Extensive changes to utilize compiled code debugging information:

* The stack parser now knows how to parse individual compiled code
subproblem frames.

* The compiler-info package has been updated to match the new compiled
code info format.

* The environment abstraction has been generalized to handle compiled
code stack and closure frames, when debugging info is available to
describe them.

* The `debug' and `where' presentation formats have been adjusted
somewhat to allow compiled code information to be presented
reasonably.

* `debug' has been extended to provide the common `A' command from
`where'; there should be little need to invoke `where' from `debug'.