This patch is an expansion of my earlier patch,
#1410119, and should be considered to supersede it.

This patch fixes a reference leak in the earlier
implementation of foldr. The reference leak was tricky
to trigger, but existed.

In addition, this patch breaks the functional module
into two parts: Modules/_functionalmodule.c and
Lib/functional.py. The latter is for list-producing
functions which are better implemented as generators
(to make them lazier), while the former is reserved for
non-list-producing functions, written in C for speed.
Lib/functional.py imports the `_functional` module
generated from Modules/_functionalmodule.c.

The total contents of the functional module:
+ compose
+ concat
+ concatMap
+ cycle
+ drop
+ dropWhile
+ flip
+ foldl
+ foldl1
+ foldr
+ foldr1
+ id
+ iterate
+ partial
+ repeat
+ scanl
+ scanl1
+ scanr
+ scanr1
+ take
+ takeWhile

In addition to a full test-suite and latex-formatted
documentation for all functions, this patch also adds a
functional/ directory to Demo/ and populates it with
examples.

After applying this patch, the existing
Modules/functionalmodule.c should be removed and
replaced with the attached _functionalmodule.c (sorry,
I couldn't figure out how to make this show up in an
svn diff reliably).

The patch is against svn revision 42148.