prepare release 3.2.1

prepare release 3.2.1

* Fixed gh-issue #88: Unable to run test suite (Remi Collet)
* Fixed gh-issue #86: test failure with curl 7.64
* Fixed gh-issue #85: [-Wformat-extra-args] build warnings
* Fixed gh-issue #84: segfault and build failure since curl 7.62
* Fixed gh-issue #82: Test harness improvements (Chris Wright)
* Fixed gh-issue #64: compress and connecttimeout interfere with low_speed_limit (@rcanavan)
* Fixed http\QueryString::getGlobalInstance()
* Fixed missing 2nd reflection argument info of http\Client::notify()
* Fixed PHP-7.4 compatibility