patch 9.1.0617: Cursor moves beyond first line of folded end of buffer

patch 9.1.0617: Cursor moves beyond first line of folded end of buffer

Problem:  Cursor moves beyond start of a folded range at the end of a buffer.
Solution: Move cursor to start of fold when going beyond end of buffer.
          Check that cursor moved to detect FAIL in outer cursor function.
          (Luuk van Baal)

closes: #15344

Signed-off-by: Luuk van Baal <luukvbaal@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>