[Libreoffice] gbuild: filter module

hi all,

i'm sitting on patches to convert the filter module to gbuild.

these could land in a git repo near you soon if somebody gave me an fdo
account :)

because this is based on patches for ApacheOOo most of the new files
have the standard ASF/AL2 license boilerplate.  i'd like to leave that
as is, because i'm lazy and it doesn't make that much sense to me to
replace it with MPL/whatever when the same code is available elsewhere
as AL2.  except of course if there is some requirement or policy here
that i'm currently not aware of :)

also, tested only on Linux because that's all i can build at home.

regards,
 michael