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/quickfix.txt b/runtime/doc/quickfix.txt
index 8662854..5879727 100644
--- a/runtime/doc/quickfix.txt
+++ b/runtime/doc/quickfix.txt
@@ -935,11 +935,11 @@
 "$*" can be given multiple times, for example: >
    :set makeprg=gcc\ -o\ $*\ $*
 
-The 'shellpipe' option defaults to ">" for the Amiga, MS-DOS and Win32.  This
-means that the output of the compiler is saved in a file and not shown on the
-screen directly.  For Unix "| tee" is used.  The compiler output is shown on
-the screen and saved in a file the same time.  Depending on the shell used
-"|& tee" or "2>&1| tee" is the default, so stderr output will be included.
+The 'shellpipe' option defaults to ">" for the Amiga and Win32.  This means
+that the output of the compiler is saved in a file and not shown on the screen
+directly.  For Unix "| tee" is used.  The compiler output is shown on the
+screen and saved in a file the same time.  Depending on the shell used "|&
+tee" or "2>&1| tee" is the default, so stderr output will be included.
 
 If 'shellpipe' is empty, the {errorfile} part will be omitted.  This is useful
 for compilers that write to an errorfile themselves (e.g., Manx's Amiga C).
@@ -1384,9 +1384,9 @@
 following the rest of the line is matched.  If "%f" is followed by a '%' or a
 backslash, it will look for a sequence of 'isfname' characters.
 
-On MS-DOS, MS-Windows and OS/2 a leading "C:" will be included in "%f", even
-when using "%f:".  This means that a file name which is a single alphabetical
-letter will not be detected.
+On MS-Windows a leading "C:" will be included in "%f", even when using "%f:".
+This means that a file name which is a single alphabetical letter will not be
+detected.
 
 The "%p" conversion is normally followed by a "^".  It's used for compilers
 that output a line like: >