www/firefox-esr: update to 45.7.0 (rc1)

Changes: https://www.mozilla.org/firefox/45.7.0/releasenotes/
Changes: https://hg.mozilla.org/releases/mozilla-esr45/shortlog
Security: e60169c4-aa86-46b0-8ae2-0d81f683df09
MFH: 2017Q1