language, ANSI C, enum constants must be representable as ints.
We assumed at-least-33-bit ints. This worked on some 32-bit
systems because we don't mix negative sysinit enum constants with
too-large sysinit enum constants, and the compiler used an unsigned
32-bit type for sysinit enum variables, so sysinit enum variables
were sorted correctly. The fix lops off 4 hopefully-unused bits
so that we now only assume at-least-29-bit ints.