Bug#723045: dolfin: FTBFS on several architectures

[peter green]

>Dear maintainer(s), please note that dolfin's Build-Depends appears to be uninstallable on several architectures atm.
I'm not one of the maintainers of this package but I would note that the installability issue seems to be caused by dolfin 
build-depending on an obsolete slepc dev package libslepc3.2-dev while the current slepc dev package is libslepc3.4.2-dev.