Detect integer overflow (CVE-2016-9063)
Detect integer overflow (CVE-2016-9063)

Needs XML_CONTEXT_BYTES to be _undefined_ to trigger,
default is defined and set to 1024.

Previously patched downstream, e.g.
https://sources.debian.net/src/expat/2.2.0-2/debian/patches/CVE-2016-9063.patch/
https://bug1274777.bmoattachments.org/attachment.cgi?id=8755538

This version avoids undefined behavior from _signed_ integer overflow.

Signed-off-by: Pascal Cuoq <b00284d5a7c66750c5aa4fb04d87aca0ae105e4e@trust-in-soft.com>

libexpat/libexpat,libexpat/libexpat,libexpat/libexpat,libexpat/libexpat,libexpat/libexpat,libexpat/libexpat