compiler.h: add QEMU_ALIGNED() to enforce struct alignment

Reviewed-by: Sergey Fedorov <sergey.fedorov@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Message-Id: <1465412133-3029-2-git-send-email-cota@braap.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>

include/qemu/compiler.h

@@ -41,6 +41,8 @@
 # define QEMU_PACKED __attribute__((packed))
 #endif
 
+#define QEMU_ALIGNED(X) __attribute__((aligned(X)))
+
 #ifndef glue
 #define xglue(x, y) x ## y
 #define glue(x, y) xglue(x, y)