uniformally use __ varients for attribute names

Otherwise, debug code such as "void __attribute__((noreturn)) foobar()" fails
to compile when the noreturn itself gets expanded, resulting in
__attribute__((__attribute__((noreturn)))).

No function change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

xen/include/xen/compiler.h

@@ -11,12 +11,12 @@
 #define unlikely(x)   __builtin_expect(!!(x),0)
 
 #define inline        __inline__
-#define always_inline __inline__ __attribute__ ((always_inline))
-#define noinline      __attribute__((noinline))
+#define always_inline __inline__ __attribute__ ((__always_inline__))
+#define noinline      __attribute__((__noinline__))
 
-#define noreturn      __attribute__((noreturn))
+#define noreturn      __attribute__((__noreturn__))
 
-#define __packed      __attribute__((packed))
+#define __packed      __attribute__((__packed__))
 
 #if (!defined(__clang__) && (__GNUC__ == 4) && (__GNUC_MINOR__ < 5))
 #define unreachable() do {} while (1)
@@ -43,7 +43,7 @@
 #define __inline__ __inline__ __init
 #endif
 
-#define __attribute_pure__  __attribute__((pure))
+#define __attribute_pure__  __attribute__((__pure__))
 #define __attribute_const__ __attribute__((__const__))
 
 /*
@@ -60,7 +60,7 @@
 #define __used         __attribute__((__used__))
 #define __maybe_unused __attribute__((__unused__))
 
-#define __must_check __attribute__((warn_unused_result))
+#define __must_check __attribute__((__warn_unused_result__))
 
 #define offsetof(a,b) __builtin_offsetof(a,b)