Move extern "C" {} to eb.p, it's only needed for the prototypes.

Also delete the duplicated prototypes that were in both eb.p and ebjs.p.
These actually became separate declarations, the one in ebjs.p never being used.
Fortunately eb.p was included first, so that declaration won the day,
which is the one we wanted.
Anyways, these are only declared once now, so no confusion.