doc: Remove refs to dos(16|32), win16, and win95

This is primarily low-hanging fruit; there are still many references to
things such as MS-DOS throughout (see os_dos.txt).

src/nvim/ex_cmds2.c

@@ -2992,12 +2992,8 @@ void ex_checktime(exarg_T *eap)
 
 static char *get_locale_val(int what)
 {
-  char        *loc;
-
-  /* Obtain the locale value from the libraries.  For DJGPP this is
-   * redefined and it doesn't use the arguments. */
-  loc = setlocale(what, NULL);
-
+  // Obtain the locale value from the libraries.
+  char *loc = setlocale(what, NULL);
 
   return loc;
 }