Add pecl-mongodb to php5
Add pecl-mongodb to php5

This leaves mongodb on php7 unchanged, and leaves `mongo` on php5
(thus meaning that php5 has both mongo and mongodb

PHP5 versions:  5.5.36 ; 5.5.37 ; 5.6.22 ; 5.6.23

[#119012029]

chregu/cf-php-varnish-buildpack,cloudfoundry/php-buildpack,cf-identity/php-buildpack,LeonidLe/php-buildpack,chregu/cf-php-varnish-buildpack,LeonidLe/php-buildpack,cloudfoundry/php-buildpack,tgemal00/php-buildpack,nkatre/php-buildpack,LeonidLe/php-buildpack,jan-randis/php-db2-mysql-buildpack,Orange-OpenSource/cf-php-build-pack,chregu/cf-php-varnish-buildpack,LeonidLe/php-buildpack,chregu/cf-php-varnish-buildpack,tgemal00/php-buildpack,chregu/cf-php-varnish-buildpack,cf-identity/php-buildpack,jan-randis/php-db2-mysql-buildpack,nkatre/php-buildpack,tgemal00/php-buildpack,cloudfoundry/php-buildpack,cloudfoundry/php-buildpack,nkatre/php-buildpack,Orange-OpenSource/cf-php-build-pack,chregu/cf-php-varnish-buildpack,jan-randis/php-db2-mysql-buildpack,cf-identity/php-buildpack,cf-identity/php-buildpack,tgemal00/php-buildpack,nkatre/php-buildpack,jan-randis/php-db2-mysql-buildpack,jan-randis/php-db2-mysql-buildpack,nkatre/php-buildpack,Orange-OpenSource/cf-php-build-pack,LeonidLe/php-buildpack,cloudfoundry/php-buildpack,nkatre/php-buildpack,cloudfoundry/php-buildpack,tgemal00/php-buildpack,LeonidLe/php-buildpack,cloudfoundry/php-buildpack,tgemal00/php-buildpack,cf-identity/php-buildpack,cf-identity/php-buildpack,cf-identity/php-buildpack,jan-randis/php-db2-mysql-buildpack