PythonGlue: return NULL when throwing a exception
PythonGlue: delete replay on early return
PythonGlue: clarify PyList_Append checks and return NULL on error
PythonGlue: only encode valid enl values
PythonGlue: return empty string if list to encode has no elements
PythonConverters: only one altitude reading is obligatory
DouglasPeuckerMod: return early if only one fix to classify
PythonGlue: check if start time is smaller then end time
Event/Kobo/Queue: move RotatePointer instance into class MergeMouse

Apply the rotation before the bounds checks.  There was a big Kobo
regression in portrait mode: the bounds were applied before the mouse
position was rotated, and thus we had everything clipped at y<600
instead of y<800.

As a side effect, this feature is now available on all "console"
targets.  It will allows us to rotate the screen even if the graphics
driver doesn't support it.