Fix freetype build

[SimonSapin]

Pick up servo/libfreetype2#3

r? @Manishearth

[hoppipolla-critic-bot]

Critic review: https://critic.hoppipolla.co.uk/r/3196

This is an external review system which you may optionally use for the code review of your pull request.

In order to help critic track your changes, please do not make in-place history rewrites (e.g. via git rebase -i or git commit --amend) when updating this pull request.

[Manishearth]

r+

[SimonSapin]

@bors: retry

[bors-servo]

saw approval from Manishearth
at SimonSapin@6ed83b5

[bors-servo]

merging SimonSapin/servo/fix-freetype-build = 6ed83b5 into auto

[bors-servo]

SimonSapin/servo/fix-freetype-build = 6ed83b5 merged ok, testing candidate = a957349

[bors-servo]

some tests failed:
failure: http://build.servo.org/builders/linux/builds/669

[bors-servo]

saw approval from Manishearth
at SimonSapin@6ed83b5

[bors-servo]

merging SimonSapin/servo/fix-freetype-build = 6ed83b5 into auto

[bors-servo]

SimonSapin/servo/fix-freetype-build = 6ed83b5 merged ok, testing candidate = bd4f94a

[bors-servo]

all tests pass:
success: http://build.servo.org/builders/linux/builds/672
success: http://build.servo.org/builders/mac1/builds/214
success: http://build.servo.org/builders/mac2/builds/214

[bors-servo]

fast-forwarding master to auto = bd4f94a