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.

man/fr/Makefile.am

@@ -53,6 +53,16 @@ if !USE_PAM
 man_MANS += $(man_nopam)
 endif
 
+man_subids = \
+	man1/newgidmap.1 \
+	man1/newuidmap.1 \
+	man5/subgid.5 \
+	man5/subuid.5
+
+if ENABLE_SUBIDS
+man_MANS += $(man_subids)
+endif
+
 EXTRA_DIST = \
 	$(man_MANS) \
 	man1/id.1 \
@@ -62,5 +72,9 @@ if USE_PAM
 EXTRA_DIST += $(man_nopam)
 endif
 
+if !ENABLE_SUBIDS
+EXTRA_DIST += $(man_subids)
+endif
+
 include ../generate_translations.mak