libelf: Also copy/convert partial datastructures in xlate functions

libelf: Also copy/convert partial datastructures in xlate functions

The generated xlate functions can only convert full datastructures,
dropping any trailing partial data on the floor. That means some of
the data might be undefined. Just copy over the trailing bytes as
is. That data isn't really usable. But at least it is defined data.

https://sourceware.org/bugzilla/show_bug.cgi?id=29000

Signed-off-by: Mark Wielaard <mark@klomp.org>