* Adopt upb change for timestamp and duration json to php
* Remove unused code
* Re-sync upb
* Fix php implementation timestamp json parsing
* Fix strptime use local timezone on mac.
* Remove succeeding tests
* Resync
* Add tests for values
* Fix php tests
* Fix encoder handlers change default value
Previously, oneofsubmsg_handler and submsg_handler change zval's default value directly.
The fix use REPLACE_ZVAL_VALUE which create a copy of parsed value and assign it to zval.
* Add conformance test for php c back
php c extension has different result for conformance test for different
php version and architecture. Try to add conformance back for php 7.1 c extension first.
* Disable conformance test for c extension on 32-bit architecture
32-bit and 64-bit have different failing tests
* Fix typo
Paul Yang
Bo Yang
Feng Xiao
Jack Wakefield
Jisi Liu
Yilun Chong