Test against 8.0.0rc1

This should fix the remaining test failures.

Author: nikic

.travis.yml

@@ -35,7 +35,7 @@ matrix:
     - name: PHP 8.0 Code on PHP 7.0 Integration Tests
       php: 7.0
       script:
-        - test_old/run-php-src.sh 8.0.0beta4
+        - test_old/run-php-src.sh 8.0.0rc1
   allow_failures:
     - name: PHP 8.0 Code on PHP 7.0 Integration Tests
   fast_finish: true