__progname should be const char*, not char*.

Change-Id: I8e846872c30a712fbc05c8da59ffa1cec1be31a4
diff --git a/libc/unistd/syslog.c b/libc/unistd/syslog.c
index 3571d59..7878475 100644
--- a/libc/unistd/syslog.c
+++ b/libc/unistd/syslog.c
@@ -46,7 +46,7 @@
 
 static struct syslog_data sdata = SYSLOG_DATA_INIT;
 
-extern char	*__progname;		/* Program name, from crt0. */
+extern const char	*__progname;		/* Program name, from crt0. */
 
 static void	disconnectlog_r(struct syslog_data *);	/* disconnect from syslogd */
 static void	connectlog_r(struct syslog_data *);	/* (re)connect to syslogd */