Remove extra debuggin gsupport that is turned on for head but turned off

Remove extra debuggin gsupport that is turned on for head but turned off
for stable branches:

	- shift to MALLOC_PRODUCTION
	- turn off automatic crash dumps
	- remove kernel debuggers, INVARIANT*[1], WITNESS* from GENERIC
	  kernel config files

[1] INVARIANT* left on for ia64 at least temporarily, marcel@ will test
    to see if they are still required as they had been for stable/8.

Approved by:	re (implicit)

git-svn-id: svn://svn.freebsd.org/base/stable/9@226405 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f