pam_start.c: call bindtextdomain() to expose Linux-PAM locales

Without the change locales are not visible to applications using PAM if
PAM library is installed into a --prefix= different from the default
one.

configure.ac

@@ -676,6 +676,7 @@ AM_CONDITIONAL(ENABLE_GENERATE_PDF, test -n "$FO2PDF")
 
 AM_GNU_GETTEXT_VERSION([0.18.3])
 AM_GNU_GETTEXT([external])
+AC_CHECK_FUNCS(bindtextdomain)
 AC_CHECK_FUNCS(dngettext)
 
 AH_BOTTOM([#ifdef ENABLE_NLS

libpam/Makefile.am

@@ -3,6 +3,7 @@
 #
 
 AM_CFLAGS = -DDEFAULT_MODULE_PATH=\"$(SECUREDIR)/\" -DLIBPAM_COMPILE \
+	-DLOCALEDIR=\"$(localedir)\" \
 	-I$(srcdir)/include $(LIBPRELUDE_CFLAGS) $(ECONF_CFLAGS) \
 	-DPAM_VERSION=\"$(VERSION)\" -DSYSCONFDIR=\"$(sysconfdir)\" \
 	$(WARN_CFLAGS)

libpam/pam_start.c

@@ -25,6 +25,21 @@ static int _pam_start_internal (
     D(("called pam_start: [%s] [%s] [%p] [%p]"
        ,service_name, user, pam_conversation, pamh));
 
+#ifdef HAVE_BINDTEXTDOMAIN
+    /* Bind text domain to pull in PAM translations for a case where
+       linux-pam is installed to non-default prefix.
+
+       It is safe to call bindtextdomain() from multiple threads, but it
+       has a chance to have some overhead. Let's try to do it once (or a
+       small number of times as `bound_text_domain` is not protected by
+       a lock. */
+    static int bound_text_domain = 0;
+    if (!bound_text_domain) {
+	bound_text_domain = 1;
+	bindtextdomain(PACKAGE, LOCALEDIR);
+    }
+#endif
+
     if (pamh == NULL) {
 	pam_syslog(NULL, LOG_CRIT,
 		   "pam_start: invalid argument: pamh == NULL");