PATCH: Add x32 to x86_64/bits/sigcontext.h

[Roland McGrath]

> This is a public header file. Do all compilers support this?

It should get an __extension__ prefix just to be pedantic.  It was a GNU
extension but is now in C11.  I don't really care if we support compilers
that don't handle the simplest basic GNU extensions that have been in GCC
for over 20 years.  If someone is concerned about that you could do:

	union
	{
	  struct _fpstate *fpstate;
	  __uint64_t __fpstate_word;
	} __fpstate_u;
# define fpstate __fpstate_u.fpstate

But that is worse in other ways.

Unless somebody else has a strong objection with good rationale,
I think we can use the anonymous union feature in public headers.


Thanks,
Roland