lpy.el (lpy-line-left-p): Improve special position detection

[EugeneNeuron]

More consistent result for edge cases:

• when (current-column) is multiple of 4, but should be special

  x = (",".join(["1", "2"])
      | .startswith("1"))
  

• point in multiline sting is no longer special.

  test = """
  |content
  """
  

  test = """
   | content
  """
  

• point at bolp can now be special, if last command is not lpy-space/newline.

  if x = 2:
  |    print(x)