Convert existing die(..., strerror(errno)) to die_errno()

Change calls to die(..., strerror(errno)) to use the new die_errno().

In the process, also make slight style adjustments: at least state
_something_ about the function that failed (instead of just printing
the pathname), and put paths in single quotes.

Signed-off-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-unpack-objects.c

@@ -68,7 +68,7 @@ static void *fill(int min)
 		if (ret <= 0) {
 			if (!ret)
 				die("early EOF");
-			die("read error on input: %s", strerror(errno));
+			die_errno("read error on input");
 		}
 		len += ret;
 	} while (len < min);