buffer not long enough for 2kbit rsa keys resulting in truncated
reads from ctl file.

Notes:
Tue Nov 4 18:59:07 EST 2008 geoff
    done differently: eliminated buf and put result straight into a.


Reference: /n/sources/patch/applied/rsa2kctl
Date: Tue Nov  4 01:21:25 CET 2008
Signed-off-by: quanstro@quanstro.net
Reviewed-by: geoff

--- /sys/src/cmd/auth/factotum/fs.c	Tue Nov  4 01:21:19 2008
+++ /sys/src/cmd/auth/factotum/fs.c	Tue Nov  4 01:21:17 2008
@@ -452,7 +452,7 @@
 static int
 keylist(int i, char *a, uint n, Fsstate *fss)
 {
-	char buf[512];
+	char buf[4096];
 	Keyinfo ki;
 	Key *k;