Also, remove assumption that if something is opaque that it
must be in the UniformConstant storage class.
This allows function declarations to know all parameters will
be in the Function storage class.
This modifies function parameter passing to pass the counter
buffer associated with a struct buffer to a function as a
hidden parameter. Similarly function declarations will have
hidden parameters added to accept the associated counter buffers.
There is a limitation: if a SB type may or may not have an associated
counter, passing it as a function parameter will assume that it does, and
the counter will appear in the linkage whether or not there is a counter
method used on the object.
