Earlier versions of the bandstructure code had terrible 
convergence problems, which resulted in the need to set
very high values of parameters BS_MAX_CG_STEPS and BS_MAX_ITER.

Special case code to increase the defaults in a task-dependent
way for phonon tasts was implemented in parameters_read.  With
the new Hamiltonian module this is no longer necessary, and the 
special case code can now be removed.

Perhaps it can be removed for MAGRES DFPT calculations too - ask Jonathan.

The custom defaults to elec_energy_tol should stay however, as we
still nned the accurate density from the initial SCF calculation.