Apologies, the original patch is incorrect because define-abbrev
requires passing :count as a keyword argument unlike the obsolete
calling convention.

Attached is a new patch, which unfortunately does not preserve the old
abbrev file writing format. However, any recent version of Emacs will
be able to accept this format for define-abbrev, and the previously
written abbrev file format is documented as obsolete, so now is as
good a time as any.