patch 7.4.1008
Problem:    The OS/2 code pollutes the source while nobody uses it these days.
Solution:   Drop the support for OS/2.
diff --git a/src/ex_cmds.c b/src/ex_cmds.c
index 73a5564..f3cb4b4 100644
--- a/src/ex_cmds.c
+++ b/src/ex_cmds.c
@@ -1570,7 +1570,7 @@
     char_u	*buf;
     long_u	len;
 
-#if (defined(UNIX) && !defined(ARCHIE)) || defined(OS2)
+#if defined(UNIX) && !defined(ARCHIE)
     int		is_fish_shell;
     char_u	*shell_name = get_isolated_shell_name();
 
@@ -1590,7 +1590,7 @@
     if (buf == NULL)
 	return NULL;
 
-#if (defined(UNIX) && !defined(ARCHIE)) || defined(OS2)
+#if defined(UNIX) && !defined(ARCHIE)
     /*
      * Put braces around the command (for concatenated commands) when
      * redirecting input and/or output.