18.104.22.168: Catch errors during compile-time-too processing.
* Errors signaled within an (EVAL-WHEN (:COMPILE-TOPLEVEL) ...),
i.e. during ``compile-time-too' processing, are now caught and
reported just like errors at macroexpansion time.
Previously, we landed in the debugger from within the compiler and
thus provided pretty much no information about the actual source
context to the user.
Now, we won't land in the debugger, and the appropriate source
context is reported along the error.
* Some slight generalization in the test suite.
* So we can add tests for errors in EVAL-WHEN and during
Tobias C. Rittweiler