[firedrake] Prescribe pressure at a corner for Darcy's equation

[Lawrence Mitchell]

> On 7 Feb 2017, at 09:03, Lawrence Mitchell <lawrence.mitchell at imperial.ac.uk> wrote:
> 
> 
> PETSc.Options("foo_").getAll()
> 
> => {"bar": "-baz_bar"}
> 
> I will push a fix for this one.

Please try the branch proposed here:

https://github.com/firedrakeproject/firedrake/pull/1004

Lawrence