id: with -Z, show SMACK security context

Adds an optional dependency on libsmack.

* m4/jm-macros.m4: Look for the smack library/header.
* src/id.c (main): Output the smack context if available.
* src/local.mk: Link with libsmack if available.
* NEWS: Mention the new feature.

1 files changed, 2 insertions, 0 deletions

diff --git a/NEWS b/NEWS
index 3edb946af..ae6251de2 100644
--- a/NEWS
+++ b/NEWS
@@ -20,6 +20,8 @@ GNU coreutils NEWS                                    -*- outline -*-
 
 ** New features
 
+  id -Z reports the SMACK security context where available.
+
   join accepts a new option: --zero-terminated (-z). As with the sort,uniq
   option of the same name, this makes join consume and produce NUL-terminated
   lines rather than newline-terminated lines.