Bug#635192: provide O_CLOEXEC on kfreebsd-*

[Petr Salinger <Petr.Salinger@seznam.cz>]

Hi.

Both wheezy kernels (8.3 and 9.0) do support O_CLOEXEC.
Together with enabling O_CLOEXEC we have to
at least raise minimal kernel version to 8.3 in

  debian/debhelper.in/libc.preinst
  debian/sysdeps/kfreebsd.mk

We have to wait before buildd receives new kernel,
as current (squeezy one) does not suffice.

Petr