www/drupal7: Update from 7.51 to 7.52

Changelog: https://www.drupal.org/blog/drupal-823-and-752-released

Also remove CONFLICTS_INSTALL because drupal7 and drupal8 install
their files into different directories.

PR: 214813
Submitted by: Jochen Neumeister (maintainer)
Approved by: mentors (implicit)
MFH: 2016Q4
Security: CVE-2016-9449
Security: CVE-2016-9450
Security: CVE-2016-9451
Security: CVE-2016-9452
Security: https://vuxml.freebsd.org/freebsd/8db24888-b2f5-11e6-8153-00248c0c745d.html