xpp: Do not typedef bool on RHEL 5.2 or later.

Without digging into the specifics, it looks like Red Hat Linux 5.9
removed the hex_asc definition that was previously used to determine
if the bool definition was backported.

We can simply use the RHEL_RELEASE_CODE now since we do not support any
releases before the 5 series now.

Reported-By: Vladimir Mikhelson
Internal-Issue-ID: DAHLIN-312
Signed-off-by: Shaun Ruffell <sruffell@digium.com>
Acked-By: Tzafrir Cohen <tzafrir.cohen@xorcom.com>
dahdi: Initialize the channels cdev structure.

This is necessary to prevent a crash when opening files by the new
device files, which do not have a valid file_operations structure.
This fixes a problem does not exist in any releases of DAHDI.

Since none of the existing tools or applications open files from the
new location of /dev/dahdi/channels/<span>/<offset>, this wasn't
seen until just recently.

Reported-by: Ted Gerold <ted@twg.org>
Signed-off-by: Shaun Ruffell <sruffell@digium.com>