MSAA doesn't work in Linux

[erikd71]

Hi there and thanks for this very useful library!

I found an issue where MSAA doesn't work in Linux's implementation of GLCanvas.
Looking at the code, it seems that GLData.samples and GLData.sampleBuffers are ignored in method PlatformLinuxGLCanvas.create().
I could get it to work by adding the following lines in that method:

		if (attribs.samples > 0) {
			attrib_list.put(GLX14.GLX_SAMPLE_BUFFERS).put(1);
			attrib_list.put(GLX14.GLX_SAMPLES).put(attribs.samples);
		}

I think this is in line with the javadoc and what the Windows implementation does, and I've tested this on 2 machines (one with an Intel GPU and one with AMD).
It would be great if this could be fixed in the next release!

Cheers,
Erik