combinatorics -- lame overflow with Compositions(n).count() (very easy to fix)

[was]

The following calculation is trivial, so shouldn't overflow:

sage: len(Compositions(30))
536870912
sage: len(Compositions(40))
Traceback (most recent call last):
...
OverflowError: long int too large to convert to int

This is also lame:

sage: len(Partitions(1000))
Traceback (most recent call last):
...
OverflowError: long int too large to convert to int

[was]

This is also

[was]

This is caused by a stupid limitation in Python's len. Use .count, etc. instead.