freetype2 to 2.7.1

[Andriy Gapon]

It would be really courteous to add an UPDATING entry about this update.
Specifically, because of the important changes between 2.6.5 and 2.7 as
described here:
https://lists.gnu.org/archive/html/freetype-announce/2016-09/msg00000.html

Not everyone follows freetype development and announcements, and some users were
already quite surprised (including myself).

P.S.
Perhaps it would be worthwhile explicitly mentioning
FREETYPE_PROPERTIES=truetype:interpreter-version=35

-- 
Andriy Gapon