compiler: Add compiler noinline attribute and barrier helper

They are not needed at moment but will be needed at
parasite/restorer code rework time, so add them now
just to not forget.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: Pavel Emelyanov <xemul@parallels.com>

include/compiler.h

@@ -27,12 +27,18 @@
 # define always_inline		__always_inline
 #endif
 
+#ifndef noinline
+# define noinline		__attribute__((noinline))
+#endif
+
 #define __aligned(x)		__attribute__((aligned(x)))
 
 #ifndef offsetof
 # define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
 #endif
 
+#define barrier()		asm volatile("" ::: "memory")
+
 #define container_of(ptr, type, member) ({			\
 	const typeof( ((type *)0)->member ) *__mptr = (ptr);	\
 	(type *)( (char *)__mptr - offsetof(type,member) );})