standardize scroll check in a few places

Dependencies

• [2] ODLKHO7B switch to line index in a function
• [3] PX7DDEMO autosave slightly less aggressively
• [4] IRCKL6VN extract scrolling logic out of insert_at_cursor
• [5] PFT5Y2ZY move
• [6] 2ZYV7D3W handle tab characters
• [7] G6OYAYHU paste in text with M-v
• [8] DRFE3B3Z mouse buttons are integers, not strings
• [9] BYG5CEMV support for naming points
• [10] GN3IF4WF bugfix: pasting newlines
• [11] 3TDOZESE extract scrolling logic out of insert_return
• [12] SQLVYKVJ rename
• [13] LF7BWEG4 group all editor globals
• [14] 73OCE2MC after much struggle, a brute-force undo
• [15] SPSW74Y5 add state arg to Text.keychord_pressed
• [16] 3MAZEQK5 add state arg to Text.textinput
• [17] Z5HLXU4P add state arg to a few functions
• [18] UHB4GARJ left/right margin -> left/right coordinates
• [19] XNFTJHC4 split keyboard handling between Text and Drawing
• [20] QCPXQ2E3 add state arg to a few functions
• [21] VJ77YABH more efficient undo/redo
• [22] 5UG5PQ6K undo commit 861c57b533
• [*] BULPIBEG beginnings of a module for the text editor

Change contents

• replacement in text.lua at line 159
  [3.37]→[3.236:302](∅→∅),[3.28]→[3.236:302](∅→∅)
  − if State.cursor_y >= App.screen.height - State.line_height then
  [3.37]

  [2.64]
  + if State.cursor_y > App.screen.height - State.line_height then
• replacement in text.lua at line 183
  [3.192]→[3.192:261](∅→∅)
  − if (State.cursor_y + State.line_height) > App.screen.height then
  [3.192]

  [3.15259]
  + if State.cursor_y > App.screen.height - State.line_height then
• replacement in text.lua at line 192
  [3.509]→[3.652:720](∅→∅),[3.195]→[3.652:720](∅→∅)
  − if State.cursor_y >= App.screen.height - State.line_height then
  [3.509]

  [2.135]
  + if State.cursor_y > App.screen.height - State.line_height then