[Bug-readline] Use of autoheader

[Burton, Ross]

Hi,

I'd like to propose dropping the hand-maintained config.h.in and
instead use autoheader, adding the description parameters to
configure.ac as required.

As an example of why I think this should happen, grep the source tree
for STRUCT_DIRENT:

aclocal.m4:AC_DEFINE(HAVE_STRUCT_DIRENT_D_INO)
aclocal.m4:AC_DEFINE(HAVE_STRUCT_DIRENT_D_FILENO)
aclocal.m4:AC_DEFINE(HAVE_STRUCT_DIRENT_D_NAMLEN)
config.h.in:#undef STRUCT_DIRENT_HAS_D_INO
config.h.in:#undef STRUCT_DIRENT_HAS_D_FILENO
configure.in:BASH_STRUCT_DIRENT_D_INO
configure.in:BASH_STRUCT_DIRENT_D_FILENO
posixdir.h:#  if defined (HAVE_STRUCT_DIRENT_D_NAMLEN)
posixdir.h:#  endif /* !HAVE_STRUCT_DIRENT_D_NAMLEN */
posixdir.h:#if defined (HAVE_STRUCT_DIRENT_D_INO) && !defined
(HAVE_STRUCT_DIRENT_D_FILENO)
posixdir.h:#if !defined (HAVE_STRUCT_DIRENT_D_INO) || defined
(BROKEN_DIRENT_D_INO)
posixdir.h:#if defined (HAVE_STRUCT_DIRENT_D_INO) && !defined
(BROKEN_DIRENT_D_INO)
posixdir.h:#if defined (D_INO_AVAILABLE) || defined
(HAVE_STRUCT_DIRENT_D_FILENO)

aclocal.m4 and posixdir.m4 both think that the symbols are called
HAVE_STRUCT_DIRENT_D_*, but config.h.in is using STRUCT_DIRENT_HAS_*.
This means the generated config.h doesn't set either of the symbols,
and this code which should be executed isn't.

The quick fix is to correct the mistakes in config.h.in, but I'd be
willing to adapt a patch set that we've been carrying for some time to
add the required extra parameters to aclocal.m4/configure.ac so that
autoheader can work if you'd accept it.

Ross