Add a spec for FFI::Struct's field of type "callback that takes callbacks as parameter"
Add a spec for FFI::Struct's field of type "callback that takes callbacks as parameter"

ffi/ffi,tduehr/ffi,ferventcoder/ffi,MikaelSmith/ffi,yghannam/ffi,MikaelSmith/ffi,sparkchaser/ffi,majioa/ffi,mvz/ffi,tduehr/ffi,sparkchaser/ffi,yghannam/ffi,mvz/ffi,MikaelSmith/ffi,majioa/ffi,yghannam/ffi,ferventcoder/ffi,tduehr/ffi,yghannam/ffi,mvz/ffi,yghannam/ffi,sparkchaser/ffi,majioa/ffi,tduehr/ffi,sparkchaser/ffi,mvz/ffi,ffi/ffi,majioa/ffi,ferventcoder/ffi,ffi/ffi,MikaelSmith/ffi,ferventcoder/ffi