Update Travis to PHP up to 8.1

PHP 5.3 is broken due to Letsencrypt certificate cannot download composer

PHP 5.4 do not contains apc module on (and precise has same cert problem than 5.3))

Author: Tybaze

.travis.yml

@@ -1,29 +1,37 @@
 os: linux
-dist: xenial
+dist: focal
 language: php
 
 php:
-    - 7.0
-    - 7.1
-    - 7.2
-    - 7.3
-    - 7.4
-    - nightly
+  - 7.4
+  - 8.0
+  - 8.1
+  - nightly
 
 # run build against nightly but allow them to fail
 jobs:
     fast_finish: true
     allow_failures:
         - php: nightly
+        - php: 5.3
+        - php: 5.4
     include:
         - php: 5.3
           dist: precise
         - php: 5.4
-          dist: precise
+          dist: trusty
         - php: 5.5
           dist: trusty
         - php: 5.6
           dist: trusty
+        - php: 7.0
+          dist: xenial
+        - php: 7.1
+          dist: xenial
+        - php: 7.2
+          dist: xenial
+        - php: 7.3
+          dist: xenial
 
 services:
     - memcached