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-fsck.c

@@ -225,15 +225,15 @@ static void check_unreachable_object(struct object *obj)
 						&type, &size);
 				if (buf) {
 					if (fwrite(buf, size, 1, f) != 1)
-						die("Could not write %s: %s",
-						    filename, strerror(errno));
+						die_errno("Could not write '%s'",
+							  filename);
 					free(buf);
 				}
 			} else
 				fprintf(f, "%s\n", sha1_to_hex(obj->sha1));
 			if (fclose(f))
-				die("Could not finish %s: %s",
-				    filename, strerror(errno));
+				die_errno("Could not finish '%s'",
+					  filename);
 		}
 		return;
 	}