Allow setting a MinVersion, stating from which OpenCL version a
builtin function is available, and a MaxVersion, stating from which
OpenCL version a builtin function should not be available anymore.
Guard some definitions of the "work-item" builtin functions according
to the OpenCL versions from which they are available.
Add the "vector data load and store" builtin functions (e.g. vload/vstore),
whose signatures differ before and after OpenCL 2.0 in the pointer
argument address spaces.
Patch by Pierre Gondois and Sven van Haastregt.
Would it make sense to rename this to CLAny or CLAll instead? Although do we even need to add a name for this or may be rather keep as numeric value representing default initialization?