Port r16319 (22e0380)

Original commit message:
By setting this flag assertions behind --debug-code will trigger a
breakpoint instead of a call into Abort. This eases debugging, as the
call site is less cluttered and the backtrace starts where it should.

BUG=

Patch from Balazs Kilvady <kilvadyb@homejinni.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16342 ce2b1a6d-e550-0410-aec6-3dcde31c8c00