Changes

Use gluegen's JUnit in Eclipse

This fixes problems when Eclipse's default JUnit is too old for our code.

Start adding texture interop test.

The test here is still not complete, just checking in so I can switch
branches.

Finish texture sharing test.

Make the test modify a GL texture with a CL kernel, then loop over the
texture afterwards to check each texel has the right value. Also make
the test loop over all platforms and devices that support sharing.

Fix CL-GL interoperability tests on Mac.

Fixed detection of compatible interoperability platforms (was silently
skipping platform because GL vendor was Nvidia, but CL vendor was
Apple). Also fixed CL kernel syntax error about signed-unsigned
comparison that ATI's driver on Windows didn't find, and fixed the CL
memory object to be write-only instead of read-only (which ATI's Windows
driver just ignored).