yet another bugfix. But for how long?

Dependencies

• [2] 3OKKTUT4 up and down arrow now moving by screen line where possible
• [3] 242L3OQX bugfix: ensure Cursor_line is always on a text line
• [4] TRNWIQN6 more precise height calculation when scrolling up as much as possible while keeping cursor on screen
• [*] BULPIBEG beginnings of a module for the text editor

Change contents

• replacement in text.lua at line 384
  [2.767]→[2.767:832](∅→∅)
  − local h = 20 + Drawing.pixels(Lines[Screen_top1.line-1].h)
  [2.767]

  [2.832]
  + local h = 20 + Drawing.pixels(Lines[top2.line-1].h)