Use int (ioctl)(...) rather than int ioctl(...) so that ioctl can be defined

as a macro w/o messing things up.  This is really an abuse and we will back
this out as soon as the abusers have been fixed.  Add a comment to this
effect.

With this change, the XFree86-4 port now builds.

sys/sys/ioccom.h

@@ -67,7 +67,12 @@
 #include <sys/cdefs.h>
 
 __BEGIN_DECLS
-int	ioctl(int, unsigned long, ...);
+/*
+ * use parens around the ioctl so that people can define ioctl as a macro.
+ * Note: This will go away in the future, as soon as the current abusers
+ * have been fixed.
+ */
+int	(ioctl)(int, unsigned long, ...);
 __END_DECLS
 
 #endif