These can be used internally by

  call self%set_private(name, value)

   or

  call self%get_private(name, value)

but are not valid for the self%set()/get() routines, i.e. are not
visible to users of ELPA.

The public "solve" method has been renamed "eigenvectors" since it
computes the eigenvalues and (at least parts of) the eigenvectors

Another routine "eigenvalues" will just compute the eigenvalues

DATATTYPE instead of DATATYPE

This prevented builing for SUSE Leap_42.2 but actually this should
always have failed !

Since there are at the moment no double-valued entries, it is better to
abort early than to try to walk the zero-length array. It might even
work, but better safe than sorry.