Add missing warning in doc
Found by Nicholas Wilson
fixes #288
diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index 6e9d8f3..68153ef 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -1246,6 +1246,8 @@
* If set, the X509 parser will not break-off when parsing an X509 certificate
* and encountering an unknown critical extension.
*
+ * \warning Depending on your PKI use, enabling this can be a security risk!
+ *
* Uncomment to prevent an error.
*/
//#define MBEDTLS_X509_ALLOW_UNSUPPORTED_CRITICAL_EXTENSION