make log4moz not depend on constants.js so it's easier to reuse it in another project

services/sync/modules/log4moz.js

@@ -44,7 +44,19 @@ const Cr = Components.results;
 const Cu = Components.utils;
 
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
-Cu.import("resource://weave/constants.js");
+
+const MODE_RDONLY   = 0x01;
+const MODE_WRONLY   = 0x02;
+const MODE_CREATE   = 0x08;
+const MODE_APPEND   = 0x10;
+const MODE_TRUNCATE = 0x20;
+
+const PERMS_FILE      = 0644;
+const PERMS_DIRECTORY = 0755;
+
+const ONE_BYTE = 1;
+const ONE_KILOBYTE = 1024 * ONE_BYTE;
+const ONE_MEGABYTE = 1024 * ONE_KILOBYTE;
 
 const Log4Moz = {};
 Log4Moz.Level = {};