expat: upgrade 2.4.1 -> 2.4.2

Changelog:
=========
  #509 #510  Link againgst libm for function "isnan"
  #513 #514  Include expat_config.h as early as possible
       #498  Autotools: Include files with release archives:
               - buildconf.sh
               - fuzz/*.c
  #507 #519  Autotools: Sync CMake templates
  #495 #524  CMake: MinGW: Fix pkg-config section "Libs" for
               - non-release build types (e.g. -DCMAKE_BUILD_TYPE=Debug)
               - multi-config CMake generators (e.g. Ninja Multi-Config)
  #502 #503  docs: Document that function XML_GetBuffer may return NULL
               when asking for a buffer of 0 (zero) bytes size
  #522 #523  docs: Fix return value docs for both
               XML_SetBillionLaughsAttackProtection* functions
  #525 #526  Version info bumped from 9:1:8 to 9:2:8;
               see https://verbump.de/

 for what these numbers do

Signed-off-by: Wang Mingyu <wangmy@fujitsu.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 98a87bcf)
Signed-off-by: Anuj Mittal <anuj.mittal@intel.com>