bugfix: autosave and undo in a couple of cases

Dependencies

• [2] 7SFHSB47 rename
• [3] 65XHTZEK regression: couldn't do many drawing operations because line.y was reset
• [*] OTIBCAUJ love2d scaffold
• [*] XNFTJHC4 split keyboard handling between Text and Drawing
• [*] 252M2QMD forgot to move this special case out
• [*] BYG5CEMV support for naming points

Change contents

• edit in main.lua at line 451
  [3.457]

  [6.4979]
  + local drawing_index, drawing = Drawing.current_drawing()

  + local before = snapshot(drawing_index)
• edit in main.lua at line 454
  [6.5015]

  [7.3]
  + record_undo_event({before=before, after=snapshot(drawing_index)})

  + save_to_disk(Lines, Filename)
• edit in main.lua at line 472
  [8.556]

  [2.48]
  + local before = snapshot(Lines.current_drawing_index)
• edit in main.lua at line 482
  [8.899]

  [8.899]
  + record_undo_event({before=before, after=snapshot(Lines.current_drawing_index)})