www/firefox-esr: update to 45.8.0 (rc1)

Changes: https://www.mozilla.org/firefox/45.8.0/releasenotes/
Changes: https://hg.mozilla.org/releases/mozilla-esr45/shortlog
Security: 96eca031-1313-4daf-9be2-9d6e1c4f1eb5
MFH: 2017Q1