Auto merge of #582 - staktrace:featurified, r=glennw
Auto merge of #582 - staktrace:featurified, r=glennw

Export the servo-freetype-sys feature from webrender

See commit message for why this is needed.

I tested this to ensure that in the Firefox build we can opt-in to the codegen feature but NOT freetype-lib. The servo build seems to also be ok with this change (I cherry-picked this patch to the version of webrender that servo is currently using, and used [replace] to make servo use the modified version with this patch). The sample library in webrender also builds fine with this change, since servo-freetype-sys is enabled in the default configuration. If there's more testing needed please let me know.

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servo/webrender,servo/webrender,servo/webrender,servo/webrender,servo/webrender,servo/webrender