patch 8.2.0017: OS/2 and MS-DOS are still mentioned

Problem:    OS/2 and MS-DOS are still mentioned, even though support was
            removed long ago.
Solution:   Update documentation. (Yegappan Lakshmanan, closes #5368)
diff --git a/runtime/doc/vi_diff.txt b/runtime/doc/vi_diff.txt
index 741003d..a7a6c2b 100644
--- a/runtime/doc/vi_diff.txt
+++ b/runtime/doc/vi_diff.txt
@@ -1,4 +1,4 @@
-*vi_diff.txt*   For Vim version 8.2.  Last change: 2019 Nov 12
+*vi_diff.txt*   For Vim version 8.2.  Last change: 2019 Dec 17
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -136,11 +136,7 @@
 	- All Unix systems (it works on all systems it was tested on, although
 	  the GUI and Perl interface may not work everywhere).
 	- Amiga (500, 1000, 1200, 2000, 3000, 4000, ...).
-	- MS-DOS in real-mode (no additional drivers required).
-	- In protected mode on Windows 3.1 and MS-DOS (DPMI driver required).
-	- Windows 95 and Windows NT, with support for long file names.
-	- OS/2 (needs emx.dll)
-	- Atari MiNT
+	- Windows NT, with support for long file names.
 	- VMS
 	- BeOS
 	- Macintosh