This fixes an issue in which comparison operators (e.g. <, ==)
in lambda expressions would return the wrong result type causing
compilation errors.
Also adds a few test cases to ensure the correct result type
and that lambda expressions can be properly used with count_if().
refs kylelutz/compute#9
device, context, and queue are initialized statically in `context_setup.hpp`.
With this change all tests are able to complete when an NVIDIA GPU is in
exclusive compute mode.
Side effect of the change:
Time for all tests to complete reduced from 15.71 to 13.03 sec Tesla C2075.