Key changes:
- Typing echo notifications back in ns_draw_window_cursor (on EmacsView,
synchronous with cursor draw — this is how v9 did it and it worked)
- Rich userInfo: AXTextEditType=3, AXTextChangeValues with actual char
- SelectedTextChangedNotification on every cursor draw
- Full text protocol on EmacsView: accessibilityNumberOfCharacters,
accessibilitySelectedText, accessibilityInsertionPointLineNumber,
accessibilityVisibleCharacterRange, accessibilityLineForIndex:,
accessibilityRangeForLine:, accessibilityAttributedStringForRange:
- accessibilityAttributedStringForRange: on EmacsAccessibilityBuffer too
- Virtual tree kept for VoiceOver window/buffer detection