Fixed the docstring for calendar.isleap() function.

Thanks Boštjan Mejak for the patch.

Lib/calendar.py

@@ -95,7 +95,7 @@ def __len__(self):
 
 
 def isleap(year):
-    """Return 1 for leap years, 0 for non-leap years."""
+    """Return True for leap years, False for non-leap years."""
     return year % 4 == 0 and (year % 100 != 0 or year % 400 == 0)