New patch, fixing issue pointed out by gutworth and some others that came up.

I've used the following as a test input:

-----8<----------8<--------
#!/usr/bin/python
def x():
  """
  This is a doc
  """
  '''
  Another doc.'''
  s = """line one
line two
      line three
      '''
line five
"""
  var = '''test'''
  """Third doc"""
  return s
-----8<----------8<--------

The patch got way bigger than the initial version and feels a little hackish, but I couldn't come up with something better.