Fix problems found by Coverity.

Fix problems found by Coverity.

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.