Revert "Synthesize GDEF glyph class for any glyph that does not have one in GDEF"

This reverts commit 69f9fbc4200442a35484d3c790ae8f4979be5d60.

See https://github.com/behdad/harfbuzz/issues/347#issuecomment-268873401
Fixes https://github.com/behdad/harfbuzz/issues/347
2 files changed