lalswig_test.i: functions should not be static
LALDetChar: fix double-free in gsequence-wrapping code

- Do not free LALGSequenceIter* from within XLALGSequenceNext(), as this
  interacts badly with SWIG's parent tracking for XLALGetGSeqSnglBurst().
  Instead XLALGSequenceNext() returns a boolean, indicating whether iteration
  should continue, and calling (C) code must free iterator themselves.
  (Python code will free the iterator automatically once it is no longer needed.)
LALDetChar: add SWIG RETURNS_PROPERTY directive to XLALGSequenceBegin()

- To prevent gsequence being freed until its iterators are also freed
LALDetChar: add missing 'winner' argument to write_round_xml()

- To match call from laldetchar-hveto