Add php 7.1.6 and 7.0.20, remove php 7.1.4 and 7.0.18
Add php 7.1.6 and 7.0.20, remove php 7.1.4 and 7.0.18

- Add httpd 2.4.26, remove 2.4.25
- Rebuild all phps for new cassandra driver

[#146754721 #146685849 #147136505 #147405177]

cf-identity/php-buildpack,cf-identity/php-buildpack,cf-identity/php-buildpack,cf-identity/php-buildpack,cloudfoundry/php-buildpack,cf-identity/php-buildpack,cloudfoundry/php-buildpack,Orange-OpenSource/cf-php-build-pack,cloudfoundry/php-buildpack,cf-identity/php-buildpack,cloudfoundry/php-buildpack,Orange-OpenSource/cf-php-build-pack,cloudfoundry/php-buildpack,cf-identity/php-buildpack,cloudfoundry/php-buildpack,cloudfoundry/php-buildpack,Orange-OpenSource/cf-php-build-pack