updated for version 7.4.684
Problem:    When starting several Vim instances in diff mode, the temp files
            used may not be unique. (Issue 353)
Solution:   Add an argument to vim_tempname() to keep the file.
diff --git a/src/quickfix.c b/src/quickfix.c
index abb4a6e..186520a 100644
--- a/src/quickfix.c
+++ b/src/quickfix.c
@@ -2945,7 +2945,7 @@
 
     if (*p_mef == NUL)
     {
-	name = vim_tempname('e');
+	name = vim_tempname('e', FALSE);
 	if (name == NULL)
 	    EMSG(_(e_notmp));
 	return name;