[PATCH] sparc64 rusage build fix

Some patch in -mm causes the sparc64 build to explode because `struct rusage'
isn't defined or declared in compat.h.   So forward-declare it.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/compat.h

@@ -18,6 +18,8 @@
 #define compat_jiffies_to_clock_t(x)	\
 		(((unsigned long)(x) * COMPAT_USER_HZ) / HZ)
 
+struct rusage;
+
 struct compat_itimerspec { 
 	struct compat_timespec it_interval;
 	struct compat_timespec it_value;