patch 8.0.1751: #ifdef causes bad highlighting

Problem:    #ifdef causes bad highlighting.
Solution:   Move code around. (Ozaki Kiichi, closes #2731)
diff --git a/src/ui.c b/src/ui.c
index 87f3c1e..9c25638 100644
--- a/src/ui.c
+++ b/src/ui.c
@@ -1854,18 +1854,15 @@
     len = 0;	/* to avoid gcc warning */
     for (try = 0; try < 100; ++try)
     {
-#  ifdef VMS
-	len = vms_read(
-#  else
-	len = read(read_cmd_fd,
-#  endif
-	    (char *)inbuf + inbufcount, (size_t)((INBUFLEN - inbufcount)
+	size_t readlen = (size_t)((INBUFLEN - inbufcount)
 #  ifdef FEAT_MBYTE
-		/ input_conv.vc_factor
+			    / input_conv.vc_factor
 #  endif
-		));
-#  if 0
-		)	/* avoid syntax highlight error */
+			    );
+#  ifdef VMS
+	len = vms_read(read_cmd_fd, (char *)inbuf + inbufcount, readlen);
+#  else
+	len = read(read_cmd_fd, (char *)inbuf + inbufcount, readlen);
 #  endif
 
 	if (len > 0 || got_int)