AM: more of the pre-scf is executed on all workers
AM: s2_calc() does nothing on slaves, comments
AM: s2_calc() is called from a parallel context
AM: broadcast SCF convergence flag
AM: comments only
AM: rm trailing whitespace
AM: rm commented stubs
AM: comments, whitespace, rm dead code
AM: occupation_get_holes() does nothing on slaves
AM: fix typo
AM: occupation_get_holes() is called from par context

By now only the body of the SCF loop is executed in legacy master/slave mode.
Pre- and post-scf run in SPMD mode.