This changes the checks for the device type to use the bitwise-and
operator instead of the equaility operator. The returned type is a
bitset and this would cause errors when multiple bits were set.
This fixes a bug on POCL which returns the device type as a
combination of CL_DEVICE_TYPE_DEFAULT and CL_DEVICE_TYPE_CPU. Now
the correct device type (device::cpu) is detected for POCL.
This cleans up the example code. Now all of the examples use
the "namespace compute = boost::compute" alias. This shortens
the example code making it less verbose and more clear. Also
cleans up a few style issues.
