use %m printf specifier where appropriate

function                                             old     new   delta
out                                                   85      75     -10
udhcpd_main                                         1472    1461     -11
open_stdio_to_tty                                     98      85     -13
init_exec                                            245     232     -13
udhcpc_main                                         2763    2749     -14
do_cmd                                              4771    4755     -16
status_line_bold_errno                                32      14     -18
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/7 up/down: 0/-95)             Total: -95 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/selinux/matchpathcon.c b/selinux/matchpathcon.c
index e57120d..6945a02 100644
--- a/selinux/matchpathcon.c
+++ b/selinux/matchpathcon.c
@@ -104,7 +104,7 @@
 			freecon(con);
 			continue;
 		}
-		printf("actual context unknown: %s, should be ", strerror(errno));
+		printf("actual context unknown: "STRERROR_FMT", should be " STRERROR_ERRNO);
 		error += print_matchpathcon(path, 1);
 	}
 	matchpathcon_fini();