[cmap] Don’t reject subtables with surrogate pairs
[cmap] Don’t reject subtables with surrogate pairs

They are still valid fonts, though it might not be the best practice
Unicode-compliance wise.

Fixes #80.

davelab6/ots,irori/ots,anthrotype/ots,khaledhosny/ots,anthrotype/ots,davelab6/ots,irori/ots