This fixes a few issues encountered when using iterators with a
void value_type (e.g. std::insert_iterator<>).
The is_contiguous_iterator meta-function was refactored to always
return false for iterators with a void value_type and avoid
instantiating types for containers with a void value_type
(e.g. std::vector<void>::iterator) which previously resulted
in compilation errors.
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.
