x32: Add struct ucontext_x32

Add a definition for struct ucontext_x32; this is inherently a mix of
the 32- and 64-bit versions.
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>

arch/x86/include/asm/ia32.h

@@ -43,6 +43,15 @@ struct ucontext_ia32 {
 	compat_sigset_t	  uc_sigmask;	/* mask last for extensibility */
 };
 
+struct ucontext_x32 {
+	unsigned int	  uc_flags;
+	unsigned int 	  uc_link;
+	stack_ia32_t	  uc_stack;
+	unsigned int	  uc__pad0;     /* needed for alignment */
+	struct sigcontext uc_mcontext;  /* the 64-bit sigcontext type */
+	compat_sigset_t	  uc_sigmask;	/* mask last for extensibility */
+};
+
 /* This matches struct stat64 in glibc2.2, hence the absolutely
  * insane amounts of padding around dev_t's.
  */