Revision 472727

www/firefox: update to 61.0

- Drop DTRACE option, as it no longer builds
  https://bugzilla.mozilla.org/show_bug.cgi?id=1448659
  https://bugzilla.mozilla.org/show_bug.cgi?id=702179#c33
- Stop using system hunspell per
  https://bugzilla.mozilla.org/show_bug.cgi?id=1460600

Changes:	https://www.mozilla.org/firefox/61.0/releasenotes/
PR:		227850
Security:	cd81806c-26e7-4d4a-8425-02724a2f48af
MFH:		2018Q2
Differential Revision:	https://reviews.freebsd.org/D15227