The id_t type used to pass IDs to wait6(2) and procctl(6) is a 64-bit
integer. Fix the argument decoding to treat this as a quad instead of an
int. This includes using QUAD_ALIGN and QUAD_SLOTS as necessary. To
continue printing IDs in decimal, add a new QuadHex argument type that
prints a 64-bit integer in hex, use QuadHex for the existing off_t arguments,
repurpose Quad to print a 64-bit integer in decimal, and use Quad for id_t
arguments.

This fixes the decoding of wait6(2) and procctl(2) on 32-bit platforms.