[RFA 2/3] libctf: Add configure check for asprintf (for MinGW)

[Nick Alcock]

On 2 Jan 2020, Joel Brobecker told this:

> From: Eli Zaretskii <eliz@gnu.org>
>
> This commit fixes a compilation warning when compiling libctf
> on MinGW:
>
>     libctf/ctf-dump.c:118:8: warning: implicit declaration of function
>     'asprintf'; did you mean 'vasprintf'? [-Wimplicit-function-declaration]
>
> 	 if (asprintf (&bit, " %lx: [slice 0x%x:0x%x]",
> 	     ^~~~~~~~
> 	     vasprintf
>
> MinGW doesn't provide that function, so we depend on the one provided
> by libiberty. However, the declaration is guarded by HAVE_DECL_ASPRINTF,
> which we do not have in libctf's config.h.
>
> libctf/ChangeLog:
>
> 	PR binutils/25155:
> 	* configure.ac: Add AC_CHECK_DECLS([asprintf]).
> 	* configure, config.h.in: Regenerate.

Looks good.