`@sizeOf` returns 0 for comptime types

This defines `@sizeOf` to be the runtime size of a type, which means
that it is zero for types such as comptime_int, type, and (enum
literal).

See #2209
fb2acaff06Andrew Kelley committed on 4/25/2019, 2:31:53 AMparent733c547
4 files changedLine totals unavailable