Don't panic if UUIDs or LUIDs are wrong size

[kenba]

The change for issue #14 returns UUIDs or LUIDs for the relevant device param names.

The current implementation gets the values as a Vec<u8> then copies them into arrays of the appropriate size, i.e.: [u8; CL_UUID_SIZE_KHR] and [u8; CL_LUID_SIZE_KHR], so far so good.

The issue is that the library will panic if a device returns the wrong size for a UUID or LUID, either from the explicit assert or in the call to copy_from_slice.

This is wrong: the library shouldn't panic on bad data from a device, it should just return a Result error value.

[kenba]

The fix for the issue is to get UUIDs or LUIDs explicitly as values using CL_UUID_SIZE_KHR and CL_LUID_SIZE_KHR as the appropriate size parameter when calling clGetDeviceInfo.

Not only does this no longer panic, but it also only calls clGetDeviceInfo once instead of twice: once to get the size and then again to get the data. It also saves copying the data from the Vec<u8> into the UUID or LUID array.

Unfortunately, it was not possible to use the api_info_value! macro since the array type does not implement the Default trait.

[kenba]

Incorporated in version 0.6.1.