Change string used for plurals separation

Using \x00 proven to be bad idea as some databases (eg. SQLite) does not
cope with string containing this. Using \x1e (Record Separator) should
be safe in this regard.

Fixes #266.

trans/migrations/0036_update_unit_stats.py

@@ -23,7 +23,6 @@ import time
 from south.db import db
 from south.v2 import DataMigration
 from django.db import models
-from trans.util import PLURAL_SEPARATOR
 
 class Migration(DataMigration):
 
@@ -51,7 +50,7 @@ class Migration(DataMigration):
                 checksum=unit.checksum,
                 ignore=False
             ).exists()
-            unit.num_words = len(unit.source.split(PLURAL_SEPARATOR)[0].split())
+            unit.num_words = len(unit.source.split('\x00\x00')[0].split())
             unit.save()
             done += 1
             if done % 1000 == 0:

trans/util.py

@@ -52,7 +52,7 @@ AVATAR_DEFAULT_IMAGE = getattr(
     'identicon'
 )
 
-PLURAL_SEPARATOR = '\x00\x00'
+PLURAL_SEPARATOR = '\x1e\x1e'
 
 
 def avatar_for_email(email, size=80):