class specialization for integral types

[Charles Hixson]

How would a specialize a parameterized class to only allow integral 
parameters (i.e., anything that would respond "true" to
static if (is (T : long) )

(I'd have said "static if (is (T : cent) )" or "static if (is (T : 
ucent) )", but those are still marked "reserved for future use".)

I do want to allow byte, ubyte, etc. to be legal values.