that the common case can be handled with no hassles on all machines.
fix up the various internal variables which are also exported via sysctl
(and which therefore must be 'int's) to do the right thing via a special
read/write function.
the kernel panics. It may be initialized to 0 with the kernel option
"DDB_ONPANIC=0", and is patchable. It may be changed at run-time
from within the DDB (as a DDB variable) or via the ddb.onpanic sysctl
node.
Export all DDB built-in variables via sysctl.
