Octave 4.2.2 used for CI testing on Linux, apparently does not allow private
functions to be defined in the same file as a classdef. The files here are
simply the result of splitting out the private functions in osqp.m (see
https://github.com/oxfordcontrol/osqp-matlab) as of 9/1/20 (i.e. v 0.6.0).
