Zero thread structure so we don't continue with a bogus

signal.

R=rsc
APPROVED=rsc
DELTA=1  (1 added, 0 deleted, 0 changed)
OCL=33249
CL=33296

src/libmach/linux.c

@@ -199,6 +199,7 @@ attachthread(int pid, int tid, int *new, int newstate)
 	t = malloc(sizeof *t);
 	if(t == nil)
 		return nil;
+        memset(t, 0, sizeof *t);
 
 	thr[nthr++] = t;
 	t->pid = pid;