Add BigInteger for

http://groups.google.com/group/tryton/browse_thread/thread/7753c8e3ffc4b14d

trytond/osv/fields.py

@@ -110,6 +110,13 @@ class Integer(Column):
         return ('int4', 'int4')
 
 
+class BigInteger(Integer):
+    _type = 'biginteger'
+
+    def sql_type(self):
+        return ('int8', 'int8')
+
+
 class Reference(Column):
     _type = 'reference'
     _classic_read = False
@@ -674,6 +681,7 @@ class Property(Function):
 _TYPE2CLASS = {
 }
 
-for klass in (Boolean, Integer, Reference, Char, Sha, Text, Float, Numeric,
-        Date, DateTime, Time, Binary, Selection, Many2One, One2Many, Many2Many):
+for klass in (Boolean, Integer, BigInteger, Reference, Char, Sha, Text, Float,
+        Numeric, Date, DateTime, Time, Binary, Selection, Many2One, One2Many,
+        Many2Many):
     _TYPE2CLASS[klass._type] = klass