yet another bugfix X-(

Dependencies

• [2] AQOJ62LN two bugfixes
• [3] FQURPLDA new primitives for reading/writing files
• [4] ED4Z6ORC cleaner API for file-system access
• [*] 3QNOKBFM beginnings of a test harness

Change contents

• replacement in app.lua at line 471
  [2.74]→[3.618:653](∅→∅),[3.618]→[3.618:653](∅→∅)
  − function(filename, contents)
  [2.74]

  [3.653]
  + function(path, contents)
• replacement in app.lua at line 475
  [3.788]→[3.788:842](∅→∅)
  − local f, err = App.open_for_writing(filename)
  [3.788]

  [3.842]
  + local f, err = App.open_for_writing(path)