[PATCH xserver] dix: unbreak --with-dtrace (default) on FreeBSD 11.1+

[Jan Beich]

gmake[2]: Entering directory '/path/to/xserver/dix'
/usr/sbin/dtrace -G -C -o dtrace-dix.o -s ../dix/Xserver.d .libs/atom.o ...
dtrace: failed to compile script ../dix/Xserver.d: line 26: useless declaration
gmake[2]: *** [Makefile:1007: dtrace-dix.o] Error 1

Signed-off-by: Jan Beich <jbeich at FreeBSD.org>
---
 dix/Xserver.d | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/dix/Xserver.d b/dix/Xserver.d
index f4f229d84..4a233e1f6 100644
--- a/dix/Xserver.d
+++ b/dix/Xserver.d
@@ -27,6 +27,8 @@
 #define string char *
 #define pid_t uint32_t
 #define zoneid_t uint32_t
+#elif defined(__FreeBSD__)
+#define zoneid_t id_t
 #else
 #include <sys/types.h>
 #endif