Explicitly tag every anonymous aggregate in the public headers.

Signed-off-by: Keir Fraser <keir.fraser@citrix.com>

tools/include/xen-foreign/mkchecker.py

@@ -19,6 +19,9 @@ f.write('''
 #include <stdlib.h>
 #include <stddef.h>
 #include <inttypes.h>
+
+#define __anonymous_struct __extension__ struct
+#define __anonymous_union __extension__ union
 ''');
 
 for a in archs:

tools/include/xen-foreign/mkheader.py

@@ -38,7 +38,7 @@ inttypes["x86_64"] = {
 };
 header["x86_64"] = """
 #ifdef __GNUC__
-# define __DECL_REG(name) __extension__ union { uint64_t r ## name, e ## name; }
+# define __DECL_REG(name) __anonymous_union { uint64_t r ## name, e ## name; }
 # define __align8__ __attribute__((aligned (8)))
 #else
 # define __DECL_REG(name) uint64_t r ## name