(debug): Bind load-read-function to nil; save old value
in debugger-outer-load-read-function and restore at end.
(debugger-eval-expression): Handle load-read-function
like other magic variables.
(debugger-outer-overriding-local-map): New variable.
(debug): Bind overriding-local-map to nil; save old value
in debugger-outer-overriding-local-map and restore at end.
(debugger-eval-expression): Handle overriding-local-map
like other magic variables.
neutral values. Save the outer values in debugger-last-command, etc.
Put those saved values back into effect when returning.
(debugger-eval-expression): Put the saved values into effect
while evaluating, and store modified values back into
debugger-outer-... after evaluating.
