travis: added PHP 7.4

.travis.yml

@@ -2,13 +2,14 @@ language: php
 
 php:
  - 7.3
+ - 7.4
 
 before_script:
  - phpenv config-rm xdebug.ini
  - echo | pecl install channel://pecl.php.net/yaml-2.1.0
  - git clone https://github.com/pmmp/pthreads.git
  - cd pthreads
- - git checkout 45579e1e622acd80f9c880f3a025ba3b98b8ebef
+ - git checkout e0f514dfde01c5e7e9cf94c43615918af482a45c
  - phpize
  - ./configure
  - make