KDB, KDB_TRACE in GENERICs for stable/X

[Andriy Gapon]

I would like to propose to add KDB and KDB_TRACE options to GENERIC kernel
configurations on stable branches.  I've verified that without any other
KDB-related options and without any backend configured these options do not change
any aspect of system behavior.  Any attempts to enter debugger are ignored; on
panic a panic message is printed and system reboots after that.

With the proposed options and MFC of r212964 we should be able to get a backtrace
printed in addition to a standard panic message.  This may help us in analyzing
problems during initial system installation and for systems that keep using
GENERIC after installation for various reasons.  This is especially true for
panics that result from traps like page fault in which case we don't have much
information on cause of a trap.

Presence of the proposed options in GENERIC should not affect those who include
GENERIC into their own configuration files for further extension and/or trimming.

What do you think?

-- 
Andriy Gapon