Changed TestDriver.test_recursive_launch() in test/test_deriver.py to use...

Changed TestDriver.test_recursive_launch() in test/test_deriver.py to use pycuda.compiler.DynamicSourceModule, removed xfail marker
Added a test case for pycuda.compiler.JitLinkModule: compiles and links two .cu files.
Removed test/test_jit_link.py, all further tests in test/test_deriver.py from now on
Removed bad "import pycuda.autoinit" (how did this even get there?)