Add new oid, debug.boothowto. This allows userland apps to see

how the kernel was booted and perhaps do conditional things
based upon it (sysinstall, for example, will now turn Debug mode
on automatically if boot -v was done).

Submitted by:	msmith
Suggested by:	ulf

sys/kern/init_main.c

@@ -92,6 +92,7 @@ extern	struct user *proc0paddr;
 
 struct	vnode *rootvp;
 int	boothowto = 0;		/* initialized so that it can be patched */
+SYSCTL_INT(_debug, OID_AUTO, boothowto, CTLFLAG_RD, &boothowto, 0, "");
 
 /*
  * Promiscuous argument pass for start_init()