memoize

[Andrei Alexandrescu]

I just added a higher-order function memoize to std.functional which I 
think is pretty cool. See the docs here:

http://d-programming-language.org/cutting-edge/phobos/std_functional.html#memoize
I'm also thinking of adding that cutting-edge directory as a place for 
storing documentation for commits that are in flux but not officially 
released yet.


Andrei