C samples checking for CL_HPP defines

Several C-based samples are checking for the C++-based CL_HPP_TARGET_OPENCL_VERSION define, see comment here: https://github.com/KhronosGroup/OpenCL-SDK/pull/91#discussion_r1395576205

We should change these to look for CL_VERSION_X_Y enums instead, or remove them entirely.

Start by locating the C-based samples that check CL_HPP_TARGET_OPENCL_VERSION and review the discussion linked from PR #91. Update the affected checks to use CL_VERSION_X_Y enums or remove them, and confirm that all such sample checks are consistent.

Written by the indexing model from the issue text.