Suppress warning due to shadowed variable name
Suppress warning due to shadowed variable name

When the RETURN_STR is invoked inside _clerror2string() in debug mode,
the val parameter is actually called 'ret', which causes an assignment
of ret to ret. Use the less likely name _ret within the macro to avoid
the warning.

OCL-dev/ocl-icd,OCL-dev/ocl-icd,OCL-dev/ocl-icd