heads up excel filter bits moved to sc

[Noel Power]

I moved on-masse all the excel related ooxml import filter stuff from
oox to sc ( scfilt to be precise ). This will allow us now to access
core functionality on import rather than depending solely on UNO. 
I managed to get a full build on linux, and partial ( but a least up to
sc ) for mingw & windows. It's possible some other platforms might break
so be aware.

One hack in the sc build is that I need to include the workdir/{platform
dir}/oox/inc to pick up some generated headers. Is this nuts? is there a
better way? Short of regenerating the same stuff in sc ( duplication )
or making the oox generate the files into the solver directly I see no
alternative

Noel