[PATCH] udev - mention format string escape char in man page

If we want to pass any '%' down to a program, you need to ecape it by '%%',
otherwise we try to expand it with our own format char list.

udev.8

@@ -201,6 +201,9 @@ field for the obvious reason.)
 Use the devfs style disk name for this device.
 For partitions, this will result in 'part%n'
 If this is not a partition, it will result in 'disc'.
+.TP
+.B %%
+The '%' char itself.
 .P
 .RI "A sample " udev.rules " might look like this:"
 .sp