Fix unit test bugs on Mac OS X 64-bit.

This commit fixes bugs 959 (local work size set incorrectly),
960 (concurrencyTest() throws ConcurrentModificationException)
963 (programBinariesTest() causes SIGSEGV) and 964 (builderTest()
cases CL_INVALID_VALUE). After this commit, all JOCL tests should
pass on 64-bit Mac OS X.