Use built in next() function in test_NCBIXML.py

This change is enough to run this test file unmodified
under Python 3 where iterators don't have a next method
(see the new __next__ method instead). The next function
is built in in Python 2.6 onwards

We probably need to do this elsewhere in Biopython, this
particular test file is an interesting one to start with
because running 2to3 on it takes a long time.
Python 3 ready print statement/function
Can assume BytesIO available
This was breaking on Jython 2.7a2 (Mac)
Use built in next() function in misc test_*.py

Under Python 3 need to use next(iterator) rather than
iterator.next(), and this built in function is new in
Python 2.6 (so we couldn't use it until we dropped
support for Python 2.5).
Report slow files for 2to3
Phylo.draw_graphviz: deal with API breakage in networkx-1.8 (Issue #233)
Remove Python 2.5 hack for cmath.rect
Remove Python 2.5 specific hack in Seq method tests
Eric has contributed to the forthcoming release
Remove some really old FAQ entries in the Tutorial
More usage of iterator.next() in tests that I missed...

Now using built-in function next(...) in place of next method.
Remove commented out print statements
Resolve more print statements in the unit tests.
Fixed some old-style exceptions

These had been missed as they're split over multiple lines.
Fix line endings on test_ColorSpiral.py
Fix exception class typo
Thank Josha for small fix in Tests/common_BioSQL.py

Raised during https://github.com/biopython/biopython/pull/234
Add comment about cStringIO vs StringIO problem
Tweak test_SeqIO_QualityIO.py to allow cStringIO

Using cStringIO.StringIO("") gives a read only handle.
Using cStringIO.StringIO() gives a writeable handle.

Using StringIO.StringIO("") or StringIO.StringIO() gives
a writeable handle.