Incorporating author's latest updates

[mcg1969]

It looks like there have been two revisions or so since this GitHub repo was created. From the original site:

2017/05/06: fixed mex-functions incompatibility with Matlab 2016a
2016/10/26: fixed mex-functions incompatibility with Matlab 2015b

It would be good to incorporate those changes here, and indeed to encourage the authors to adopt the GitHub repo as canonical. Perhaps the latter is not likely but we can hope! (I have great respect for the authors bit Git can indeed be daunting for anyone new to it.)

But back to the first bit: incorporating the changes. It should be noted that we've made quite a few small but important changes that make a merge less simple. Most of them, I must admit, were stylistic, and primarily in response to the output of MATLAB's built-in linter. But some, like the use of || and && instead of | and &, are in my view more important, especially with regards to maintaining Octave compatibility. And there are some decidedly non-stylistic changes that we would seek to preserve as well.

Your mission, if you choose to accept it, is to download the latest version of SDPT3 and to gingerly merge any functional changes from that version into this repo.

[mcg1969]

Here's a start: #6