Merge branch '5.1'

* 5.1:
  Fix flaky test possiblity on PHP >=7.1

Author: nicolas-grekas

.appveyor.yml

@@ -25,7 +25,7 @@ install:
     - cd ..
     - copy /Y php.ini-development php.ini-min
     - echo memory_limit=-1 >> php.ini-min
-    - echo serialize_precision=14 >> php.ini-min
+    - echo serialize_precision=-1 >> php.ini-min
     - echo max_execution_time=1200 >> php.ini-min
     - echo date.timezone="America/Los_Angeles" >> php.ini-min
     - echo extension_dir=ext >> php.ini-min