Native bindings to the ext_atomic_counters_32 extension.

This extension adds support in the OpenCL C language for 32-bit atomic counters. Atomic counter is a device-level counter that can be added / decremented by work-items in a work-group or across work-groups executing a kernel, where the atomicity of the operation is guaranteed. The access to the counter is done only via add/dec built-in functions, and as such no two workitems will see the same value returned in the case that a given kernel only increments or decrements the counter.

This feature is highly useful for produce/consume to unordered queues.