Remove unused variable.

	* libmisc/salt.c: Remove unused variable.
Fix typo.
Ignore generated newgidmap and newuidmap
Allow disabling of subordinate IDs.

	* configure.in: Add configure options --enable-subordinate-ids /
	--disable-subordinate-ids. Enabled by default.
	* lib/prototypes.h: Include <config.h> before using its macros.
	* lib/commonio.h, lib/commonio.c: Define commonio_append only when
	ENABLE_SUBIDS is defined.
	* lib/prototypes.h, libmisc/find_new_sub_gids.c,
	libmisc/find_new_sub_uids.c: Likewise.
	* lib/subordinateio.h, lib/subordinateio.c: Likewise.
	* libmisc/user_busy.c: Only check if subordinate IDs are in use if
	ENABLE_SUBIDS is defined.
	* src/Makefile.am: Create newgidmap and newuidmap only if
	ENABLE_SUBIDS is defined.
	* src/newusers.c: Check for ENABLE_SUBIDS to enable support for
	subordinate IDs.
	* src/useradd.c: Likewise.
	* src/userdel.c: Likewise.
	* src/usermod.c: Likewise.
	* man/Makefile.am: Install man1/newgidmap.1, man1/newuidmap.1,
	man5/subgid.5, and man5/subuid.5 only if ENABLE_SUBIDS is defined.
	* man/fr/Makefile.am: Install man1/newgidmap.1, man1/newuidmap.1,
	man5/subgid.5, and man5/subuid.5 (not translated yet).
	* man/generate_mans.mak: Add xsltproc conditionals
	subids/no_subids.
	* man/login.defs.d/SUB_GID_COUNT.xml: Add dependency on subids
	condition.
	* man/login.defs.d/SUB_UID_COUNT.xml: Likewise.
	* man/usermod.8.xml: Document options for subordinate IDs and
	reference subgid(5) / subuid(5) depending on the subids condition.
Sort references alphabetically.

	* man/newgidmap.1.xml: Sort references alphabetically.
	* man/newuidmap.1.xml: Likewise.
Manpages improvement for subordinate IDs.

	* man/newusers.8.xml: Include documentation of SUB_GID_MIN,
	SUB_GID_MAX, SUB_GID_COUNT, SUB_UID_MIN, SUB_UID_MAX,
	SUB_UID_COUNT.
	* man/useradd.8.xml: Likewise.
	* man/usermod.8.xml: Likewise.
	* man/newusers.8.xml: Document usage of /etc/subgid /etc/subuid.
	* man/useradd.8.xml: Likewise.
	* man/userdel.8.xml: Likewise.
	* man/usermod.8.xml: Likewise.
	* man/newusers.8.xml: Add references to subgid(5) and subuid(5).
	* man/useradd.8.xml: Likewise.
	* man/userdel.8.xml: Likewise.
	* man/subgid.5.xml: Sort references alphabetically.
	* man/subuid.5.xml: Likewise.
	* man/subgid.5.xml: Add references to newusers(8), useradd(8),
	userdel(8), usermod(8), user_namespaces(7).
	* man/subuid.5.xml: Likewise.