Fixed exception caused by printing CUDA program object

Hi, I found the following issue when using the CUDA API:

    >>> import reikna.cluda
    >>> api = reikna.cluda.cuda_api()
    >>> thr = api.Thread.create()
    >>> prg = thr.compile('')
    >>> print prg
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
      File "reikna/cluda/api.py", line 452, in __getattr__
        return self._thr.api.Kernel(self._thr, self._program, name, static=self._static)
      File "reikna/cluda/api.py", line 469, in __init__
        self._static = static
      File "reikna/cluda/cuda.py", line 208, in _get_kernel
        return program.get_function(name)
      File ".../pycuda/compiler.py", line 275, in get_function
        return self.module.get_function(name)
    pycuda._driver.LogicError: cuModuleGetFunction failed: not found

It looks like print tries to use ``prg.__repr__``, so prg looks for a function called "``__repr__``". I changed reikna.cluda.api.Program to inherit from object so it behaves as a "new-style class", which apparently causes it to use the default ``__repr__`` implementation instead of calling ``prg.__getattr__("__repr__")``.