[FEA] Support linking multiple versions of cuco in the same project

[sleeepyjack]

CUB and Thrust both allow for custom namespaces via e.g. CUB_NS_PREFIX and CUB_NS_POSTFIX, such that multiple shared libraries can each utilize their own copy of it (and thus different versions can safely coexist). (see NVIDIA/thrust#1401 )

cuco should also implement this feature.

[sleeepyjack]

@allisonvacanti suggested to utilize versioned inline namespaces to solve this problem:

namespace cuco {
inline namespace CUCO_VERSION {
  void foo();
} /* inline namespace CUCO_VERSION */
} /* namespace cuco */

This option requires #190 to be implemented.