Testsuite additions

[Benjamin Kosnik]

>testsuite_iterators.h is able to wrap a basic pointer as any of the 
>categories of iterator. It also checks to see if any operations are 
>performed on the iterator which should not be. By defining 
>DISABLE_ITERATOR_DEBUG the debugging features can be removed and in this 
>case the pointers should be as efficent as simple raw pointers, giving a 
>way of testing an algorithm's performance on each type of input operator.

this is in, lookks great.

-benjamin