Conditionally compile per innetgr availability

innetgr is not available/functional in uclibc, provide conditions for compilation.

Signed-off-by: Dmitry Golubovsky <golubovsky@gmail.com>

Index: linux-pam-1.1.4/modules/pam_group/pam_group.c
============================================================================
--- linux-pam-1.1.4/modules/pam_group/pam_group.c	2011-06-21 05:04:56.000000000 -0400
+++ linux-pam-1.1.4/modules/pam_group/pam_group.c	2012-08-09 21:35:06.000000000 -0400
@@ -655,8 +655,14 @@
 	    continue;
 	}
 	/* If buffer starts with @, we are using netgroups */
-	if (buffer[0] == '@')
+	if (buffer[0] == '@') {
+#ifdef HAVE_INNETGR
 	  good &= innetgr (&buffer[1], NULL, user, NULL);
+#else
+	  good = 0;
+	  pam_syslog (pamh, LOG_ERR, "pam_group does not have netgroup support");
+#endif  /* HAVE_INNETGR */
+	}
 	/* otherwise, if the buffer starts with %, it's a UNIX group */
 	else if (buffer[0] == '%')
           good &= pam_modutil_user_in_group_nam_nam(pamh, user, &buffer[1]);