Conditionally compile some kernel modules

* vmci and vsock are not needed for kernels >= 3.9, they are now in the
  mainline kernel.
* vmblock and vmsync are not needed in kernels >= 3.0. vmblock has been
  deprecated in favor of vmblock-fuse. vmsync is not compiled since 3.0+
  kernels support FIFREEZE/FITHAW ioctls.