trivial changes to scratchmem_lowmem

erd_scratch_mem_calc
correction to npcoeff max from 2* to 4*
HACK for int scratch mem size.  FIXME at some later date.
more 4*npcoeff patches.
more 4*npcoeff patches.
This is a rewrite of place_scratch for the fragment SCF code.  The previous
version had an incorrect behavior when the segments did not span the entire
monomer space.  The rewrite makes use of knowing w_frag_* and n_* arrays to do
fragment to segment mapping.