VKernel SMP build bug fix heads up

[Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx>]

    The changes made in HEAD today revealed a bug in the virtual kernel's
    SMP boot sequence that will lock it up, so this is a head's up that
    you also need to recompile any SMP virtual kernels you are playing with
    to get the bug fix or they won't work with the new HEAD.

    Silly me, I thought the signal mask for a signal was just (1 << signo).
    It isn't.  Some dummy in unix land 20 years ago made it (1 << (signo-1)).
    Sigh.  So I wasn't blocking SIGIO when I thought I was.

					-Matt
					Matthew Dillon 
					<dillon@backplane.com>