Add support for cache-hinted load and store operations

[gmarkall]

To-do:

• Add documentation.
• Test cases for erroneous arguments. It would be good to check for accidental use on shared or local arrays, but this may not be easy to do.
• Add additional validations as described in comments in ld_cache_operator and st_cache_operator.
• Refactor the implementation - the load and store implementations contain a lot of common code.
• Decide on whether to support complex, and work out why it presently doesn't work.

[gmarkall]

A note: these also need to work for CPointer() types as well as arrays.