Fix wrong sign with negative zero hour timediff. Fixes #63

MySQLdb/times.py

@@ -70,10 +70,14 @@ def TimeDelta_or_None(s):
             ms = ms.ljust(6, '0')
         else:
             ms = 0
+        if h[0] == '-':
+            isNegative = True
+        else:
+            isNegative = False
         h, m, s, ms = int(h), int(m), int(s), int(ms)
         td = timedelta(hours=abs(h), minutes=m, seconds=s,
                        microseconds=ms)
-        if h < 0:
+        if isNegative:
             return -td
         else:
             return td