Update the ULE scheduler + thread and kinfo structs to use int for cpuid

Update the ULE scheduler + thread and kinfo structs to use int for cpuid
rather than u_char.

To try and play nice with the ABI, the u_char CPU ID values are clamped
at 254.  The new fields now contain the full CPU ID, or -1 for no cpu.

Differential Revision:	D955
Reviewed by:	jhb, kib
Sponsored by:	Norse Corp, Inc.