Bug#718545: freecad: FTBFS against oce 0.12

[peter green]

Tags 717034 +patch
Tags 718545 +patch
Thanks

Attatched is a patch that fixes the build failure by forcing the occ 
include directory from debian/rules. The patch also contains a fix to 
the clean target.

I have tested that the package builds succesfully with this patch, that 
the resulting package can be installed and that freecad runs and 
successfully displays the application window. I have not tested beyond that.