Use testing iterator wrappers to ensure that algorithms support their stated requirements

[jaredhoberock]

Since InputIterators can't be dereferenced multiple times we shouldn't implement algorithms like copy_if(first, last, output, pred) with copy_if(first, last, first, output, pred).

In general the unit tests should check InputIterator semantic correctness.

Forwarded from http://code.google.com/p/thrust/issues/detail?id=419

[alliepiper]

This will require that #705 is addressed first.

[alliepiper]

@upsj added an implementation of a forward_iterator_wrapper in NVIDIA/thrust#1619 that restricts an iterator's API to match the forward iterator concept. It ended up getting reverted due to #705, but remains in the git history and may be useful as a starting point for this enhancement.