Multiple camera size issue

[Jeremy Laviole]

Hello,

There is a bug, that has been bothering me for quite some time. After some hours spent on it I finally found it !
I use ARToolKitPlus through JavaCPP-presets, and I had memory troubles with multiple cameras.

For some reasons there are "screenWidth" and "screenHeight" of Tracker class that are Static.
This caused memory corruption in the "arLabelingImpl" because the memory buffer associated with the memory (l_imageL)
was resized for some reason, sometimes too big without problem, or too small which caused crashes.

I found a fix, which I will upload for my JavaCPP-presets fork :  https://github.com/poqudrof/javacpp-presets, and include in the
official JavaCPP presets as soon as possible, waiting for a fix directly in ARToolKitPlus.

I am new to Launchpad, and Bazaar, so... I put the fix linked with this file (minor changes in Tracker.cpp/.h )

Cheers !

Jeremy.