AM: comments and whitespace
AM: calc_Q_e() and a few others run in par context

One branch, supposedly dealing with e-potential on a 2D plane, is not
covered by testsuite. So I did my best on adapting it, but left an
ABORT() that will fire on the first parallel execution to alert the
user.
AM: comments and whitespace
AM: make dealloc_ham_solv() idempotent
AM: comments and whitespace
AM: fix comment, no more the case
AM: solv_energy_el() runs in parallel context
AM: rm trailing whitespace
AM: comments only
AM: use ..., only: ... in main_master()
AM: use ..., only: .. in build_mol_surfaces()
AM: buld_mol_surfaces() runs on all workers
AM: only call black-box progs in legacy mode

Also check that the global vars are the same on all workers.  This
should be removed once confident.
AM: rm trailing whitespace
AM: comments, formatting
AM: build_mol_surfaces() does all of the work on master only
AM: comments only
AM: use ..., only: ... in potential_calc_module
AM: comments only
AM: serial calc_poten_derive_charges() runs on master only