Add changelog entry for #3196: x509_crt max_pathlen int overflow fix

Backport of #3192

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/ChangeLog.d/max_pathlen.txt b/ChangeLog.d/max_pathlen.txt
new file mode 100644
index 0000000..ff56a4e
--- /dev/null
+++ b/ChangeLog.d/max_pathlen.txt
@@ -0,0 +1,5 @@
+Bugfix
+   * Fix undefined behavior in X.509 certificate parsing if the
+     pathLenConstraint basic constraint value is equal to INT_MAX.
+     The actual effect with almost every compiler is the intended
+     behavior, so this is unlikely to be exploitable anywhere. #3196