Autoconf 2.59d (released in 2006) [1] started promoting several macros
as not relevant for newer systems anymore, including the `AC_HEADER_DIRENT`.
This macro checks which header defines the `DIR` type. If `<dirent.h>`
is available it defines the `HAVE_DIRENT_H` symbol. Since the `<dirent.h>`
header is already checked in the `configure.ac`, this check is not needed
anymore. This macro also additionally checks for SCO Xenix (discontinued,
latest release 1989) dir and x libraries. [2]
Commit 6ed790685f introduced also
`<sys/dir.h>`. This header exists from times of UNIX System V and
provided definition of DIR type on these systems such as 4.3BSD.
Today `<sys/dir.h>` is kept for backwards compatibility and includes
the `<dirent.h>` on current systems. With `dirent.h>` present this
include is no longer required.
Refs:
[1] http://git.savannah.gnu.org/cgit/autoconf.git/tree/NEWS
[2] https://www.gnu.org/software/autoconf/manual/autoconf-2.69/autoconf.html
Remove unused dirent.h includes
The $Id$ keywords were used in Subversion where they can be substituted
with filename, last revision number change, last changed date, and last
user who changed it.
In Git this functionality is different and can be done with Git attribute
ident. These need to be defined manually for each file in the
.gitattributes file and are afterwards replaced with 40-character
hexadecimal blob object name which is based only on the particular file
contents.
This patch simplifies handling of $Id$ keywords by removing them since
they are not used anymore.
