Fix missing point information in undo

Fix missing point information in undo

* src/undo.c (record_insert): Use record_point instead of
  prepare_record, and do so unconditionally.
  (prepare_record): Do not record first change.
  (record_point): Now conditional on state before the last command.
  (record_delete): Call record_point unconditionally.
  (record_property_change): Use prepare_record.
  (record_marker_adjustments): Use prepare_record.

Addresses Bug# 21722