slow V3 configures (was Re: ICE during bootstrap.)

[Benjamin Kosnik]

>     push-current-language-on-stack
>     set-current-language-to-C++
>     test-for-cached-answer-oh-it's-there-never-mind-then
>     pop-language-from-stack
> 
> Those LANG_SAVE and LANG_RESTORE are what contribute the extra
> three-quarters of a banana.  :-)

phil perhaps you could be persuaded to revisit this problem, since it 
appears you've looked at it closely.

testing a limited subset of functions is something I'm not interested in 
exploring: historically, this type of change has been a disaster. 
Following phil's advice and changing to

   test-for-cached-answer-oh-it's-there-never-mind
   else
     push-current-language-on-stack
     set-current-language-to-C++
     test and cache
     pop-language-from-stack
   end   

seems like the best approach.

-benjamin