Must add #include <linux/version.h> to chan_phone.c?

On a fresh install of Slackware 12, and the latest asterisk 1.2 I find I must change chan_phone.c from

#include <linux/version.h>
#include <linux/ixjuser.h>


#include <linux/version.h>
#include <linux/compiler.h> (have to add this line)
#include <linux/ixjuser.h>

in order for it to compile. It is easy enough to do, but can anyone tell me why this is needed?

YAY - the latest 1.2.22 has solved this problem. From the changelog:

2007-07-11 17:15 +0000 [r74587] Joshua Colp

* channels/chan_phone.c, channels/Makefile: Use some Makefile magic
  to determine if linux/compiler.h is present. (issue #10174
  reported by francesco_r)