Build the lumped boundary mass matrix needed to apply Robin boundary conditions.
The vector facelist contains the list of the faces contributing to the mass matrix.
The optional argument nodelist contains the list of the degrees of freedom on the boundary.
See also: bim3a_rhs, bim3a_advection_diffusion, bim3a_laplacian, bim3a_reaction, bim2a_boundary_mass.
Package: bim