m file cache

[Tom Holroyd (NIH/NIMH) [E]]

Regarding the recent patch to cache path walks in kpse.cc;

There are two caches.  One for files that have been found, so their location in 
the path is known, and one for names that were searched for, but don't exist.  
Modify times are still checked on the directories every time, I think (that's 
done someplace else).

Do we want to have "rehash"?  In a production environment, I wouldn't want it wasting any time doing anything twice, and everything is stable so there's no need for cache rebuilding.  
Explicit rehashes are meant for that sort of thing, but it's easier to just restart the interpreter.  So I think rehash should go, too.

Other issues: do we really need brace expansion in the path?  That is: 
a/{b,c}/d.  I would vote to get rid of that, since it can be done in other ways 
if you really want it.  Also the !! magic could go, I doubt anybody is even 
aware of it. Variable and ~ expansion are OK.
--
Tom Holroyd, Ph.D.
I would dance and be merry,
Life would be a ding-a-derry,
If I only had a brain.
       -- The Scarecrow