CLSA-2026-1776440644 expat: Fix of 4 CVEs

CVE-2017-9233: fix external entity infinite loop in entityValueInitProcessor and entityValueProcessor - CVE-2023-52425: add reparse deferral heuristic to prevent On^2 parsing of large tokens in small buffer refills; fix buffer growth calculation - CVE-2013-0340: add billion laughs entity...