Revert "auto merge of #2584 : pcwalton/servo/binary-search, r=SimonSapin"

This reverts commit d8483d2365b234ec32478eb836fe6019bead9265, reversing
changes made to 3dedbd2719c78b636f4fd0860b07f1b53ed84c24.

Wikipedia crashes on linux after this change by attempting to index bogus glyphs.