[libxml2] Avoid spurious UBSan errors in parser.c

[Nick Wellnhofer <nwellnhof src gnome org>]

commit 474967241cdcce6d3a2fd356079571eee794ec12
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Wed May 31 16:46:39 2017 +0200

    Avoid spurious UBSan errors in parser.c
    
    If available, use a C99 flexible array member to avoid spurious UBSan
    errors.

 parser.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)
---
diff --git a/parser.c b/parser.c
index fd242aa..7d8da4f 100644
--- a/parser.c
+++ b/parser.c
@@ -1087,7 +1087,12 @@ typedef xmlDefAttrs *xmlDefAttrsPtr;
 struct _xmlDefAttrs {
     int nbAttrs;       /* number of defaulted attributes on that element */
     int maxAttrs;       /* the size of the array */
-    const xmlChar *values[5]; /* array of localname/prefix/values/external */
+#if __STDC_VERSION__ >= 199901L
+    /* Using a C99 flexible array member avoids UBSan errors. */
+    const xmlChar *values[]; /* array of localname/prefix/values/external */
+#else
+    const xmlChar *values[5];
+#endif
 };
 
 /**