Check for GPU detection support before detecting

Check for GPU detection support before detecting

When a CUDA-enabled binary was run on a node with no CUDA driver
available, a note was issued that the version of the CUDA driver is
insufficient, which was wrong.

Fixed this by separating detection of a valid CUDA driver (or OpenCL
platform) from enumerating the compatible devices. This permits a
GPU-enabled build configuration to gracefully degrade to the same
behaviour as a CPU-only build configuration.

Also suppressed more warnings about use of OpenCL API elements that
have been deprecated but which we intend to contiune to use
regardless.

Also fixed confusing name of rank_local, and replaced it with a
boolean that cleanly describes the required functionality.

Also fixed and simplified logic of printing the GPU report. The
implementation only prints details about the node of the master rank,
so there is no value in checking a variable that reflects the number
of GPUs detected across all nodes.

Fixes #2322

Change-Id: I831d3c0017dafc00f7bb82e3f71be5b122657d1e