Re: libgsf tweaks

Please open a bug report for this -- it's better for documentation and
keeping track of things.

gsf_output_memory_steal_bytes is pretty straightforward.

gsf_output_gzip_new_full is a bit less so.  Not because the
functionality is not good -- it is very reasonable -- but because
there are other fields in the gzip header that it might make sense to
add and I can't see us having _really_full and _really_really_full
versions.  I need to think about that part.

M.