PATCH: libgomp/25877: Add alloca.h header file.

[Paolo Bonzini]

>I don't see any reference to alloca in GCC's system.h
>(gcc/system.h)
>
It's strange then that GCC compiles on this machine. :-)  
ASM_FORMAT_PRIVATE_NAME uses alloca.

>But in libffi (which calls AC_FUNC_ALLOCA) I see that
>include/ffi_common.h has:
>
>/* Do not move this. Some versions of AIX are very picky about where
>   this is positioned. */
>#ifdef __GNUC__
># define alloca __builtin_alloca
>#else
># if HAVE_ALLOCA_H
>#  include <alloca.h>
># else
>#  ifdef _AIX
> #pragma alloca
>#  else
>#   ifndef alloca /* predefined by HP cc +Olibcalls */
>char *alloca ();
>#   endif
>#  endif
># endif
>#endif
>
>How about if I add AC_FUNC_ALLOCA to configure.ac and add this code
>from ffi_common.h to libgomp.h.
>  
>
Yes, that's what I meant.  (Note however that a maintainer's opinion may 
be different.  I cannot approve your patch).

Paolo