Small helper to handle USBMS on Kobo in KOReader.

KOReader implementation: backend & frontend

NOTE: Complex scripts (e.g., Indic, Arabic) are currently unsupported for technical reasons, so, while translations for those are welcome, they currently won't be visible.
That also applies to simple RTL scripts, although, those may have a better chance of being supported in the future than complex ones ;).
CJK should mostly behave, though.