Require pdepend, phploc and phpcpd

Summary:
These applications are used by the ant CI build.

The build also uses phpdox, but there are some conflictual dependencies.
If included to Composer, that would downgrade nikic/php-parser from
v2.1.1 => v1.3.0, and only install phpdox in v0.8.1.1.

As we use PHP 7.1, we want modern version of these tools.

Test Plan:

$ composer update
$ ant

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D845