longobject.c: also fix an ssize_t problem
  <a> could have been NULL, so hoist the size calc to not use <a>.

_ssl.c: under fail: self is DECREF'd, but it would have been NULL.

_elementtree.c: delete self if there was an error.

_csv.c: I'm not sure if lineterminator could have been anything other than
a string.  However, other string method calls are checked, so check this
one too.

shouldn't create a new flag when `name` is already the name of
an option flag.

is NULL, so there's no reason to do anything with it.  In the second case,
we know frame->f_exc_type is not NULL, so we can just do an INCREF.

free()ing the memory we allocate.

Get rid of a couple more context object references, fix some markup and clarify what happens when a generator context function swallows an exception.

Finish bringing SVN into line with latest version of PEP 343 by getting rid of all remaining references to context objects that I could find. Without a __context__() method context objects no longer exist. Also get test_with working again, and adopt a suggestion from Neal for decimal.Context.get_manager()