(appveyor) fix NSIS patch after appveyor NSIS upgrade

[sblaisot]

Appveyor updated NSIS in their build server image on September 07, 2017 [1] so our patch to NSIS is no longer valid and all appveyor build fail since then.
This PR updates the NSIS patch to fix appveyor CI builds.

[1] https://www.appveyor.com/updates/

[Be-ing]

AppVeyor build passed 👍

[daschuer]

Thank you.

Mac fails with unrelated:

Error: jpeg 8d is already installed

any idea?

[sblaisot]

Thanks @daschuer .
I will take a look at travis mac build.
either we need to upgrade jpeg to 9b before installing libjpeg or simply need to remove libjpeg as it is now pre-installed. I will try both a make a PR with the working solution.