Queue profiling and Device timebase equality test

[ellnor01]

Adds test to confirm that the timestamp returned from clGetEventProfilingInfo for an event on a device and a device timestamp queried from the same device are in the same timebase.

Fixes #753

Signed-off-by: Ellen Norris-Thompson [email protected]

[ellnor01]

Any more comments for this PR?

[bashbaug]

Merging as discussed in the October 1st teleconference.